That makes sense. I'm not disagreeing with your point as it is a very good point and I do find Soldier Boy's writing generally shoddy. I mean, he appeared in part of two seasons and they already had to alter his character and retcon his backstory. Something is undoubtedly broken here. So I'm not trying to debate you, only share my perspective.
Soldier Boy wants things without working for them; it's probably his most consistent trait. He's very obsessed with presenting a perfect image to the world of the ideal manly man. It made him very set in his ways, made him follow an honor code of sorts, and made being respected, being someone not to be crossed, critical to him. So, though he really wanted kids and was broken up over the choice in season 3, he still chose vengeance and expressing some significant self-loathing (which was a cool parallel to Homelander doing the same via Doppelgänger) over his son's life.
Some credit can be given to Ben here as at least he never did the predictable and easy thing: adopted Ryan and used his young, less damaged, less weird grandson as a replacement for the son he was disappointed by. Funnily, he actually seems to greatly prefer Homelander over Ryan. When it came down to it, he shed no tears and didn't hesitate at all when it came to striking and attempting to kill Ryan. He didn't even have to kill Ryan; he was told not to. A stark contrast to his angrily tearful speech to Homelander while readying to kill him after spending the night before agonizing over it. He also never cared to look for Ryan afterward, and seemingly did Homelander a favor by not trying to avenge Stormfront either. Homelander may not live up to Ben's old idealistic notion of having a son, but Ben does the bare minimum by him by never outright denying that he is his. (The video about child support was a dodge rather than a complete denial of their relationship.)
Putting aside all the incestuous subtext and Soldier Boy's parental hopes and dreams he has no hope of ever attaining, mainly because of his own faults (primarily his laziness), any loyalty he had toward Homelander was mostly due to his self-imposed honor system. The same one that had him committed to seeing Homelander dead in season 3 to fulfill his end of the bargain with Billy. Once he believed he had paid back Homelander satisfactorily in season 5, Ben was ready to leave for Bogotá.
The critical thing for me here is that he was visibly conflicted and regretful about hurting Homelander during that scene. Soldier Boy is not able to hide that he cares, but he also plainly doesn't want to. Working off of that, it makes sense for his character that he chose not to know more about Homelander. It's definitely the writers' preferences behind the lack of any characters investigating Homelander more deeply, but it can work for Soldier Boy's character, as well as Billy's to a point, imho. Both men avoid distressing things similarly by resorting to violence and mockery, squishy and emotional though they are inside. Though they both have enough information to know that Vought did something inhumane in the making of Homelander, they want to avoid knowing more because contending with those facts might make them waver in their chosen courses or, in Billy's case, result in the end goal being challenged by others (unlikely as it seems, given how the writers depict the characters a lot of the time, it would be IC for the Boys to question their goal if Billy had ever shared what Vogelbaum told him; MM gave A-Train a chance and Annie did the same for the Deep after all): Billy's to brutally kill Homelander with no second thoughts; Soldier Boy's to abandon him and all his trying complexity for a life of uncomplicated debauchery. It is inexcusable but at least for these two characters, it is partly inexcusable in an IC way rather than solely driven by the bias of the writers. Partly, because Billy has reason to want to learn more anyway, as it should be logical for him to consider that during those experiments Homelander potentially revealed a weakness. Also, Billy is not lazy like Soldier Boy is.
My read on Soldier Boy, after reading Jensen's interview about why Soldier Boy gave Homelander the V1 and after seeing the following episode, is that he wants Homelander but he is uncomfortable being around him and finds him exhausting. At least in the present; hence the V1. According to Jensen Ackles, Ben sees a future for him and Homelander. It doesn't really track with him immediately attempting to walk out on Homelander in the next episode but for me it works. Granted, I had to think about it and this is probably more headcanon than anything (including on Jensen's part). My impression is that (1) Soldier Boy wants to leave because he doesn't know how to fix Homelander and is not willing to put in the work to learn, (2) leaving means he can't get attached enough to stay, (3) not getting attached means he cannot know any more since knowing as much as he does makes leaving difficult enough already, (4) there is a fair bit of trauma driving this willful ignorance, (5) there is also a fair bit of pride and self-centered thinking driving it. All this brings me to what Jensen said about them having a future and the V1, because the V1 gives them time.
My thought is that perhaps Soldier Boy, ignorant and selfish as he is, decided that Homelander would keep well enough in the meantime given the V1. All so Ben could return to his old lifestyle and let Homelander work through his god emperor phase where Ben wouldn't have to deal with it. Then after months, years, decades, however long it'd take for Homelander to get over his current nonsense, they could reunite and Soldier Boy could try out fatherhood again. He also lies about Clara being the primary reason (I am going off what Jensen seems to believe here because no doubt that line was written to be truthful) because to tell Homelander any of this would result in irritating pushback and would also not fit the image Ben seeks to maintain. Bittersweet, overly optimistic, and certainly a way more generous take than the writing has earned. Nonetheless, that's how I've reconciled the potential of the relationship, Soldier Boy's contradictory choices and behavior, and Jensen's thoughts as well as his acting choices with what else was done and said onscreen.
