Yep I think you are right and I think I can replicate and I dont think its just windows:)

https://imgur.com/a/fpnWKhm

Another post mentioned 2x4k screens so I thought creating load might delay expected events so I set up gpu to lowest:

"echo low > /sys/class/drm/card0/device/power_dpm_force_performance_level"

Then opened 2 drm and lot of youtube videos with new tabs and keep refreshing reddit, after a minute or two got black boxes

specs here: https://pastebin.com/JXE2HFUu

EDIT: Nope its not it turns out marvel has black theme, sorry misleading comment, move along