Same issue here, and I know a few people that have it on most cases LCD, not OLED, but I funny think that's relevant.
The mechanism for turning a display off is to simply stop sending a signal.
There was a time when I cared more and actually did into it and windows 10 and 11 do have issues going into standby in in some configurations, with some hardware.
I once pinned down a console command that could actually tell you (cryptically of course) what things were going on that prevented standby or sleep.
Comes as no surprise that Linux does this better... But sadly I'm my case I couldn't use Linux.