I believe that even if shen yuan wasnt aware of it, being a closeted gay slowly pushed him towards turning into a half shut-in.
Shen Yuan never had any problems larping as sqq (at least, that's the way he sees it, because other people never thought he was the same sqq as before lol) because he was already used to being a poser. He always pushed himself to act like someone he is not, always putting a front. From what we see in the revised extras, outwardly he was always a cool and graceful person, with good social skills. And I can't say that he's that different inwardly, considering how he acts at the end of the novel to which i would call his "true self". But then, what went wrong for this perfect, handsome, CEO type of guy to turn into a half shut-in in his original life? I'd say that even though he was never deceiving people about who he is, he was always holding back his true self. Something would always be hidden behind the surface.
For example, he likes petting people on the head but after he got older, he realized that's not a socially acceptable thing for him anymore. Even with only this anecdote we can see that after growing up he started to hold back himself from harmless things he'd like to do. He started to see the borders people draw between other people. A guy can't pet another guy's head. I think that he started to uncounciously pick up on more of the lines people draw between sexuality and gender, like we all do. He was a straight guy of course and so he was supposed to act like a straight guy. He uncounciously kept parts of him hidden away, parts that could be considered motherly and feminine. Parts of him that are also not so straight and gender conforming.
But that's a tiring thing to do. Being in the closet, no matter when you become aware of the tight space you are in, is tiring. You put walls around yourself knowingly or unknowingly and keep getting further away from both yourself and other people. He never planned to be a shut-in, but he probably just became used to the comfort of not interacting with people as Shen Yuan, or rather as the expected version of Shen Yuan.
We can see that after he got transmigrated into PIDW he liked interacting with people, he enjoyed his friends' company. So interacting with people as Shen Yuan might be a bit tiring but now that he's not Shen Yuan anymore he again enjoys the comfort of having a disguise. But it's actually not a disguise anymore as his old self was essentially the disguise. Instead, now he starts to actually act like himself.
Shen Yuan becoming white lotus Binghe's shizun might have healed the scars in young binghe's heart, but we can argue that it also healed something in Shen Yuan. He finally got to free some of his motherly spirit, and he stopped holding back some of his desires (like petting binghe's fluffy hair, yay!) That's basically why Shen Yuan was a half shut-in in his original world but was a social butterfly in his new world. Being a shizun in a new world gave him the opportunity to get in touch with his not-so-masculine side and freeing himself from that shackle also let him get more loose and enjoy interacting with people again.
But he was still holding back something, as he was still in the closet. Realizing he was gay took some time to accept and along the way he has also hurt LBH but at the end of the novel he learnt that he doesnt have to hide or push away Luo Binghe, and he doesn't have to hide away who he is as well. Just like how bingge was influenced by masculine/heteronormative fictional worldbuilding into creating a false ideal of happiness, and shutting off parts of him that were "weak" and "fragile", Shen Yuan was also made to believe he was supposed to abandon parts of him that didn't fit in the patriarchal world view. Loving each other freed one another from caring about the expectations of society.
We could say they saved each other, from what they could be in another reality. Queer love was liberation to both of them.
At least that’s how i see things <3
[i wanted to focus on Shen Yuan's possible closet experience here, but there is this video essay that also talks about very similar topics regarding femininity and masculinity themes in SVSSS so I'm linking it here in case some people haven't watched it before.]
