I think you're underestimating how much a person can change in the span of a few years. Monobear didn't tell us till the very end just how much of our memories the program erased, but it wasn't a matter of months. It was years. Our entire time at Hope's Peak. And yeah...save for Nanami, every last one of us was involved in that group. Though, thanks to the damn program, I can't tell you the specifics as far as why. Because obviously I don't fucking remember.

[He has a guess or two as far as he goes, but...he can't really speak to any of the others. Even with his memories, he probably can't.]

Though...since you brought him up, Hinata's kind of a special case. Remember how he forgot his talent? Turns out, he never had one. He wasn't a Super High School Level, he was part of the Reserve Program. And at some point, the school decided to do some freaky-ass talent experiments on him. Only they fucked around with his head so much they ended up completely destroying his personality in the process. The guy we all got to know on the island doesn't actually exist in reality anymore.