I've seen people saying "NijJP and holoJP collab with each other all the time, why doesn't EN?". Now, that is simply not true. Random collabs between the two don't happen anymore. The only holos that frequently collab with Nijis are those that actually know each other in real life/before they even joined hololive. Haachama, Suisei, Okayu, Polka, Choco, etc. It is true for all of them. You won't see the more recent holos ever interacting with Nijis again. Starting from gen 3 pretty much none of them do.