The Yuque and the Xianzhou Alliance are ships. Yet the one that Yao Guang sent off here is a small boat carrying a single passenger. It symbolize her solo venture and taking on all the risk herself, not even calling on the army like a general should. She already gave up the commanding token by this point but if the need arise, military might would be given to her. Yet she chose to live and move as a diviner.
Fu Xuan if and when she became a general would be like Yao Guang, a general that wasn't military might focused. We haven't seen her physically on the offense so far but she is able to dance through that chaos in the Fools' Tavern. While she prefer her dance over the Sparrow Fist, her being its inheritor alone means she knows martial art. Yao Guang herself is the one that steer the small boat to the deadliest of water as well as its lone passenger. So I believe the boat metaphor is a core characteristic of her.
Fitting for a diviner that doesn't act like one and prefer to step onto the field herself, Yao Guang's most favourite hexagram isn't one that shows clear fortune or misfortune. The boat metaphor comes up again indicating she wants a peer that share with her both the extremes of fate. It's a happy coincidence that the English translation can use the phrase 'share the same boat' that matches with her symbolic boat. In JPN/VN translation, the boat didn't come up. This doesn't seem that relevant to EvanYao as one may read it right after 4.0 story and before they met properly.
The wording of ENG translation soften it, Yao Guang's tone is firmer in JPN/VIE (two languages I can personally confirm). Using the JPN script, it would be: "No, I believe you. You and I are in the same boat for not many believe the words of a diviner." Starting from this moment, Yao Guang has put her and Evan together on a boat even if it started with their shared trouble of not being believed by people. Combining the language and image, the two of them are are a 'ship/boat', a 'we' unit. She negotiated with Pearl for a right to act as she pleases alone in Planarcadia, not a collaboration. She borrowed Tingyun and acted as her mission control before sending her back to the Xianzhou Alliance. Aside from the brief shenaningan in the trailer, Tingyun carried out the mission given to her as part of the Yuque's delegation aka Yao Guang's temporary subordinate. Yao Guang put the mask on Sunday because she calculated that he can act on his own and that still would benefit her. She assisted the Astral Express during Sparxiecon but did not teamed up with them formally, going off on her own until she found her way to the Courtyard. With Evan, she didn't suggest any alliance or partnering up outright. Arguably since their thoughts are on a similar frequency, Evan can deduct Yao Guang's offer to team up through the general's advice to her and by remembering how she made a bad joke earlier because the fates of Planarcadia's people are involved. Lan's arrow couldn't kill the tree in Luofu. If Yao Guang did call it down, all she would have accomplished is the death of Planarcardians, herself and life on the planet. That is my surface reading of the joke.
When taken into account how 4.2 played out, I read it as Yao Guang already showed signs of implicit trust toward Evan there. I would translate her bad joke of a threat that if Evan does not tell her the truth then things would get out of hand bad enough Yao Guang would even call down Lan's arrow to prevent another Abundance catastrophe from happening. At the same time, that joke is a test of Evan's character. They both know Evan's tree will survive Lan's arrow so what mattered to Yao Guang is how Evan react to that possible scenario of everything being obliterated. Evan's recoil at the joke gives Yao Guang a reason to trust Evan's explanation about her own divination skill.
Yao Guang didn't ask verbally and neither did Evan say out loud her agreement. She simply went right to use 'we' to refer to the both of them. Yao Guang followed suit. Sunday refers to them as 'you two' in other language and Evan also uses 'we' rather than 'you' (Yao Guang). Sunday grouping them together is normal seeing that they work together and the wording in Eng is fine as is. It's Evan's ENG dialogue that isn't consistent with the others languages script.
Next stage which I dubbed as: shatter your partner's image that you unconsciously put on a pedestal. A crucial part in understanding one's partner and treat them as true equal rather than an expected idealized version of them in one's head. I want to say Evan was trying to impress Yao Guang here by showing her the most impressive way to travel around Planarcadia - her planet. At the same time, she likely wanted to show Yao Guang her perspective too as in what impress her in this case. As seen later during the outbreak, Evan could open up a rift in space to go right back to the Courtyard. It's safe to assume that is her method of travel if speed is needed. Since it's over in a blink of the eyes, it does not look or feel impressive but the ability to just teleport around like that is both appropriate and necessary for Evan to carry out her arbitrator duty. I think the reason Yao Guang thought there was a more impressive traveling method is due to her condition of warping around too. She both experienced how it feels to just be moved through space spontaneously and instantly. I guess I'll count that as another detail that makes them two sides of the same coin. Evan's controlled teleport gate that she can bring people with but presumably only work in Planarcadia. Yao Guang's uncontrollable self-warping that work outside of this planet. So even if Yao Guang wanted to, she can't make Evan warp with her. Thus they both can't show the other the 'cooler way of getting around' as arbitrator/general for different reasons. Curiously however for their whole time together in 4.2, Yao Guang didn't phase to another location spontaneously like she did multiple times in 4.0. Evan's ability would allow her to rush to Yao Guang's location if that happened but that would require Yao Guang to carry something that act as a beacon for Evan to recognize. Since Evan inferred Yao Guang's true intention earlier, I feel it's her own way to informally ask Yao Guang to pair up with her here with the train ticket as an excuse. In Vietnamese, a word for train is 'Tàu hỏa' (fire ship). By bringing Yao Guang here to take a train to Seafeld City with her, Evan is asking Yao Guang to join her on a ship/boat. Symbolically, that is how they formalize their partnership and the start of Yao Guang sharing a boat with someone like that divination result she most loved. If the developers were talking through Evan here then Yao Guang didn't have this kind of experience before. A layered message that requires linguistic knowledge like this is really one that an ancient being like Evan (or the almighty writers) would come up with, especially as she forcibly reincarnated a language before. Yao Guang commented that it was the first time she felt like a fool but she was smiling. She may have categorized both Evan and her as foolish for expecting too much at this point. Plus there may also be a sense of relief that she is not the one carrying everything this time as she is a fool now.
