Omg, i just did realize that it is even worse. Because it is optional and the game so linear, they are now both in a quantum state of been enemies and friends at the same time. So their friendship effectively still "ended" because they will have no big events together as friends, because that would be an event that wouldnt be impossible on the 100% route where they are no longer friends. And they also can no longer hang out with each other, because that as well would contradict their current state in the 100% route. So except maybe some lippservice, they are no longer actual friends. And that fact is what made it so easy to forget that choice was optional, because the fallout will be felt in the overall story either way.
Oh god, this really doesnt feel like it had been planned out at all.