not only that but they are completely sidelined. At the beginning they seemed to be have some sort of friendship with MC. Teammates, school mates, white knighting together etc. then step by step they were sidelined. At first, MC gave up on basketball so teammate front got lost, then they stopped showing at the school gatherings so that got lost too. Also, couple of times they refused to help MC by saying he needs to choose his fights. Tbh, that made sense. At last, turns out they were doing white knighting organized and one member of their group, side LI, got close to MC and MC basically stopped seeing them there as well. Their only interactions now, through phone out of convenience like gifting a car to MC, helping MC to access people's PC etc.
Tbh, I can't say I am against this decision of dev. Game's cast is already too crowded and cutting people where possible make sense to have some development time for important characters like ROXY. Though, one downside of it. When you start cutting off side characters, game starts to get stale because it's hard to tell a story without characters and the game slowly starts to become a fuckfest. Not there yet but it's the general direction of the game.
TLDR: Yeah, they are side characters if you mean that by BTS.