I laught when I read the names, Voodoo and Homa game are "movie bad guys level" souless hightly predatory game publishers (don't know the others). It's a PR stunt.
I'd bet that most workers would benefit from more unionisation (including those who think they're above the need for that sort of thing — think software engineers), and most small businesses would benefit from more cooperation to protect them collectively from the giants.
But organising people is _hard_ and so we tend to give up a lot of control for a little convenience. Unity can pull the rug at any time, and there's not a damn thing you can do about it. However, if 1000s of independent game developers had a share in a similar company whose constitution dictated that it was for the benefit of those independent game developers, and they could vote out directors that allowed it to deviate from that purpose, then this scenario we're seeing today would be a lot less likely.
Certainly but totally not leaded by theses companies, whose practices are the reason union should exist, a lot more than Unity. You think a 20cent fee per install is revenu cannibalization ? read one of their publisher contract.