Anyway, LG 27UP650 is indeed a great monitor. I bought it instead of LG 5K 27" which I was returning. I compared their performance side by side - and I also didn't see any difference when the monitor placed at the real life distance of ~21".
UPDATE: This LG 27UP650 just DIED. Never woke up from sleep.
Tried everything: several restarts, disconnected-reconnected every possible cable - nothing helps.
It's dead.
No picture or any signs of life at all. Worked total of 26 days.
What a disaster. So it's a second LG monitor I have to return in 2 months (after the 5K one).
So I can't use my Mac Studio. Need to disassemble, re-pack this crappy monitor, return it to Best Buy and get something different. It all becomes just insane waste of time.