Yeah, there can be a difference in terms of processing. They sometimes bypass certain processing steps in game mode which can improve input response.
It was DF's testing, yes, but I will talk with Dave tomorrow and get some more details. The numbers he provided for the KS9000 were definitely not good in HDR mode, though (as I said, over 120ms). He should have a full article with a bunch of numbers sometime this week but I'll try to get the info for you sooner.
Exaggerated for sure, it's just my personal taste. I'm also used to the Kuro which can still go darker than a VT20. The LCD glow just annoys the heck out of me, no kidding.
...but the blacks of an OLED screen? Wipes the floor with everything else that has ever been made. It's pure black. Seeing Gears 4 in that dark room just blew me away for that reason. It's really really impressive.