It's probably something simple like a contract with Twitch, but YT also has a more idiotic automated system compared to Twitch. They probably think they can get mass reported and banned off of YT far easier then Twitch, which is true to a certain extent. There's also the part where half their "talent" are or were camwhores and that doesn't fly too well with YT. Then there's the part where a bunch of them have or had channels on YT already and they didn't change any of their identities so any of their old stuff would be way easier to link to them on a YT standard.
That sounds honestly like a non-issue. You are correct about mass reporting, but it is the same on Twitch too. It feels like twitch and Vshoujo have partnership.
And about camwhore, dig into hololive, it feels like half of their talents were the same.
So yeah i agree it is probably just a contract with Twitch.
For Rushia, as far as anyone can tell, she may actually have done that. She pretty much burned all of her bridges to join Vhoejo. The most telling part was right after she was let go and everything was calming down, she made the decision to imply HL was a black company on that somewhat popular podcast thing. Then only a couple months later she's all of a sudden joining Vhoejo's "JP" branch.
Yeah, remember reaction of everyone when Coco left, fellow hololive members were borderline crying. Wasn't Fubuki actually cried.
Then Rushia left and reaction were am embodiment of a meme "Oh no. Anyway".
Still, black company... I do have suspicion that there might be some credence to this claim. With how many talents oversleep, and how protective hololive of their brand with pretty strict NDA. And i especially hate the concept of hiding identity of a streamer. Fucking corpos found the way, to dissasociate their product from the voice actor, and own you even more than before. Still from the mouth of the members, we only hear mostly a good thing, and only one person who said bad thing, sounds like a bitter idiot who got jebaited into a worse deal. So shrug.