This is something I think Phase needs to be conscious of, given the noticeable growth over the past year. Publishers aren't going to bother going after a tiny corpo full of 2views because there's nothing to gain from it, but when one of the talents is pulling in several grand a week with some of the others quickly catching up, it's only a matter of time before the corpo's on their radar.
The extra problem you have is that if the issue went to court, most vtuber gaming streams would not hold up under a Fair Dealing/Fair Use defence. It's hard to present your work as a critique or commentary on the copyrighted material when a significant part of the stream consists of off-topic discussion and interaction with chat; a less-charitable plaintiff could make the argument that a streamer is using their game footage, characters, and logos to promote their own brand and that their superchats, ad revenue etc. are ill-gotten gains - and a courtroom comprised of normies would buy it.
Most developers and publishers would be hands-off regardless, but there are always exceptions to the rule. Some don't care about the optics of taking down internet personalities (Nintendo have no need to care, they could massacre an entire village and get away with it because people like Mario, and Atlus are just terminally retarded), and others just act on impulse rather than logic. I have a bit of a fear in the back of my head that some unhinged indie developer will get mad about the Hitler particles rabbit streaming their game and take action, similar to the time the Firewatch dev DMCA'd PewDiePie because he made edgy jokes.
tl;dr if your Phase oshi's streamed a playthrough you particularly enjoy I'd recommend downloading the vods as a backup, just in case.