I think you are forgetting how original timeline mc was. This mc certainly would never forget about Steph. But it's been a big theme that og mc never really payed attention to the people around him. He was friends with steph and leo, but those were just the people he hung out at school with. From what we have been told he mostly played videogames and flet into porn.fair points. though i don't completely agree. bully viki would certainly override a lot of friendly viki. but stephi is a different story. they were a team of 3 outcasts. each of them were the oasis in a desertic social life for the others, that's very strong, especially if it helps cope with the bullying.
that desire was most likely not unrequited if we think about it. but would the resentment coming out of being "left out" of the whoring, for such a pervert as MC is, be strong enough to replace his good memories ?
he should be able to recall what she used to be like with him and leo, in my opinion.
though it's the same for his little sister. he couldn't remember that she used to want his attention so much. he could only remember her most recent behavior.
he could only remember his mother "before and after". so that might be a clue to how his mind works.
I don't think he cared that much about his social life. He only cared about cathrine and that she was out of his league in his mind. Steph and Leo were just there. He remembered Leo because they hung out longer. But he never really cared that much.
At least that was my impression.
He remembered Cathrine because she was his unrequited love. He remembered Vicky because she was his tormentor. He remembered his family, because they were family. But steph wasn't his girlfriend originally. And he didn't care that much about his friends, because videogames and porn were all that he did. She was just someone he used to be friends with and then they weren't and he didn't really care.