They can.... which everyone bitched about: they would do their cleaning cycle, no matter if you were busy or not.
Early OLEDs really did need to be pixel cleaned every 8 hours according to manufacturer estimates, the choice isn't have warning or not, its have a lifespan or not.
I don't want to blame early adopters for being early adopters, but they early adopted, and this is the early adoption problem.
But it automatically runs when it's turned off. The warning is shown because I interrupted it running early.
The warning, for my purposes, is completely useless, and only an annoyance. The automatic feature is more than enough, and I don't need to know if it was aborted early.
This is what I have done on mine, and mine as well also runs it when its off.
If your monitor is a Samsung OLED panel, yours is a near identical sibling of mine.