I was checking out some new YouTube vids & noticed this one on LGs' OLEDTV's. Their WebO/S programming options are pretty well thought-out , especially for cord-cutters , but back to the subject of display quality.....I'm noticing quite a bit of interference in their overall quality due to the background light reflections on their glass display...in particular; the reflections of windows off to the side & the reporters/viewers w/ the large window behind them...like at min 1:12 & 1:48 for example. Might help explain why LG showed-off most of their OLED flagship models in darkened rooms , as you had mentioned.
Did you happen to notice if Samsung had this same problem when you were there ? This probably has less to do with QD's or OLED's , & more to do with the reflective properties of the display screen...but it still makes a difference either way.
https://www.youtube.com/watch?v=myKnwBW3Jw0