I didn't know the U8G was doing that. Maybe sony felt like the local dimming for better contrast outweighed the need for full resolution? If I remember correctly, although a different chipset wasn't samsungs 2020 TVs turning off dimming in game mode entirely?Interesting. The U8G also disables local dimming in 4K120Hz...
Perhaps the full array stuff takes a lot of processing and has to process twice as a fast at 120hz, hence this could be the fabled bottleneck?