For what its worth, I've had the 75Q9FN since October 2018, and Game mode has always had worse local dimming performance.
It wasn't nerfed; it just took a while for people to notice.
I should also say, if you are gaming in 1440 or 1080p at 120hz, you really don't need to have the TV in Game mode to get great input lag.
At 60hz, the difference is really noticeable (I think Rtings shows 30ms decrease). At 120hz, the difference in input lag is nearly imperceptible.
Is the local dimming difference between the game-mode and normal mode that noticeable?
If so, how much?
I am really looking into buying this TV, and the main selling point is the local dimming. But if the TV does not utilize it that much in game-mode, then I don´t see it being worth it. However if it at least utilizes 50% of the full potential of the local dimming, that should be quite enough for me to buy it.
An articulated explanation on how the local dimming suffers in game mode compared to normal mode would be much appreciated!