yeah, I'll just stick to HDR10 for now. Hopefully they fix the issue. What a joke Dolby is though, just like Apple!!!
For fun I did the same comparison on my C8, and DV behaves much better but seems also brighter(nothing like on the C2). HDR10 lower range might be too dark on my C8. SDR is calibrated at 100nits.
https://www.youtube.com/watch?v=VeT3leFZ_lk
check the playback devices link in my signature.