I didn't even think apps could force the Apple TV to play in SDR if you had HDR turned on and match content off.
Spectrum app is the only app that forces SDR.
I have a Vizio TV and it takes forever to switch back from HDR to SDR, so I just left Match content and left HDR on even when looking at SDR content. But now I have to turn off the HDR all because I can't stand the whole minute it takes to get back to the home screen after using the spectrum app.
This is very annoying and it was not so when it first came out. Anyone else having this problem?