It could just be pupillary light reflex at play normalizing things a bit.
Although OLEDs aren’t potentially as bright as LED displays, they’re bright enough to cause you to squint if viewing bright enough scenes particularly in HDR mode. During normal viewing I never once felt that I needed my OLED TV to be brighter even though it wasn’t quite as bright as my non-HDR certified LED TV.
As a matter of fact my OLED performs better in my living room under bright lighting conditions probably due to the better anti-glare/reflection coating.
Performed better doesn’t necessarily mean that the TV itself was brighter. It is that I could see things easier on the screen and that takes into consideration lights as well as darks. My brain seems to like when I can clearly see the differences between the different shades of black or grey on the default Mega Bezel frame standing out on the carbon fibre background just as much as it likes to be able to resolve the brighter highlights and darker spots of a flame or lenses flare.
So I can probably understand where @BendBombBoom is coming from.
But then again it cold just be a bug or maybe the Samsung QN90A may not have been calibrated well enough out of the box.
This phenomenon between OLEDs vs even the best QDLEDs can be seen in many reviews where there are side by side comparisons. Look up a few and see how the reviewers reacted and concluded. The OLEDs usually had the most impactful image quality.