>>60589640Towa had no problems interacting with Tsuna, even brought over their friendship from her old identity and pretty much everyone from both their fanbases knows about it.
On-screen collabs with new holo identities are going to be extremely weird with the fans having to hear the same voice coming they're used to, coming from a different person. It's also not wise to allow it because it could cause the "box" to "leak" outside. This is what happened with Shigure Ui to an extent, because despite her only relation to Hololive being Subaru, she's still managed to become an "honorary holo" through her activities (not that anyone is complaining about it, just talking about the effect).
Hololive and "not hololive" is kept with a strict delineation because the brand's identity depends on the talents within it.
Some holos also choose not to interact with graduated talents because it's extremely awkward. You've referred to them as one name your entire career, and now you have to ACTIVELY remember to call them something else. Your activities after graduation also may not align well, esp. because of corporate safety issues (e.g. Kanata moving out on her own after KSon joined VShojo with Mikeneko).
The talents can still keep being friends with graduated talents in private, and even tell stories about how they hung out off stream (e.g. with Sana).
Holo talents have no issues with talking about graduations and stuff from other companies. Matsuri was beside herself when Mayuzumi announced his graduation, and iirc she also talked about Gundou sensei's graduation on twitter.
They can even visit them, say goodbyes, and wish them well on twitter. Which Niji stops them from doing (Kuzuha had to delete his Coco graduation tweet).
In this particular instance, I think they were right to delete it though. Since I agree about the distinction of the brand being important.