1. Twitch is totally within their rights to try and avoid turning their platform into some weird OnlyFans-type skin site
2. They should have 100% given the streamer the heads up on this and they should 100% make this clear in ToS instead of continuing to be incredibly vague on what they consider Twitch to be used for and not be used for.
Yep, this is pretty much my stance. I find the advent of streamers on Twitch whose channels are basically softcore OnlyFans to be kinda vaguely pathetic in a way that has nothing to do with the usual puritanical bullshit, but that in no way makes it okay for Twitch to be so capricious in how they treat their business associates - which is ultimately what these people are.
If you want your site to be some family-friendly or gamer-only environment, then spell that out and enforce it universally. But this shit where they occasionally pick out people who get the most attention or put the most heat on them, is not remotely fair. It wasn't fair when they reportedly banned DrD without telling him why (regardless of whether he's a shitheel), and it's not fair here.