The new Apple TV supports QMS VRR (Quick Media Switching, Variable Refresh Rate) so that when switching from one framerate to another (like 24 to 60Hz) there isn’t a screen blackout.
However, changing resolution or dynamic ranges, still result in blackouts. But why?
I’m thinking this is an HDMI limitation/issue, but why is this not a problem for iPhones or built in apps?
iPhone doesn’t do any of that display switching. it just uses pulldown, tone mapping, etc. same as if you turned off content matching on Apple TV (the default)