Some friendships were built for one hallway. That doesn’t make them fake. It makes them local.

Certain friendships run on shared circumstances: the same corridor, the same shift, the same bus. Take the circumstances away and there is often not much left, and that does not mean the warmth was pretend. It was real and it was local, which is a perfectly honest kind of friendship to have had.

Stop auditing your old friendships for which ones were genuine. Keep the few that survive the change and let the others be what they were. If one mattered, say so once, and let it stay in the place it belonged to.