Never forget Killua really had a very realistic gay pining with the “which is it?” line. And that he acknowledged that, if he’d ask, there’s no way to stop his feelings to come out along with everything he wanted to say.
And never forget that this next one applies to everything: back then, when he couldn’t share with Meleoron why he wasn’t kidding about shinjuu, when he held back before parting ways and shared what was safe for him to keep Gon happy and unbothered, because he was feeling already a nuisance that’s no longer useful. it’s his mindset. He’s now understanding that his feelings are important, but he can’t just share them if there’s a chance it will cause trouble to Gon right before he finally gets to meet Ging, or even cause pain, or a rejection - the worst outcome.
Putting up a smile and only letting Gon apologize about Pitou’s fight is a way to “maintain” things like they are, at least their bond. Because he’s afraid of speaking what bothers him and what he truly feels, and then changing their friendship forever. If things are this left this way and pretends everything is okay, he feels “safe” that he didn’t lose Gon and won’t touch sensitive subjects. This applies to his good and sad feelings for everything they’ve been through. If he opened, what could’ve happened? Then, he decides to looks away and let things remain untouched. If he starts sharing, he won’t be able to stop, and he’s afraid to give it a try because he’s not sure about Gon’s reaction, especially now that this love made him devote himself so profoundly.
So he leaves. He won’t face the possibility of losing him, things like they are now, “always the same”, friends, goals, journey... better to not dig them. But is it okay, really?
That’s the only fear he couldn’t pull off with the needle.
Sometimes, he can only look away, because if it shines that brightly...what could be shown by that light, that he might be wanting to hide? A light that brightens his life, saves him from dark but reveals his feelings - and his face.
At this point, it’s so close to canon that I don’t ever bother. Their love is beyond a rhetorical question.
