I think the assumption that Valve would choose user protection over getting games to work is flawed, they want openness where possible because they see it as a competitive advantage. With VAC they clearly think that maximally invasive anti-cheat isn't necessary so maybe they'll try to push providers in that direction?
Valve thinks it's not necessary and it's still in the air if it really isn't.
They have bet on the behavioral analysis anti-cheat horse but it hasn't won any races yet.
Moreover, they've proven that it's certainty more difficult to get it working than regular old fuck-the-end-user anti cheat.
Lastly, don't assume that the success of the platform will persuade these companies. They were already firmly un-persuaded when the steam deck got popular. And really, I think the popularity of a platform depends on the support of these companies more than the support of these companies depends on the popularity of a platform.
