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?
The speed of the change of TV is dependent on the TV, not the device supplying signal. TVs dont prioritize the switching and there is loads going on to match audio and video. HDMI standard supports many resolutions, if in the AppleTV select match resolution then it will convert so the TV will not have to change.