I can speak for Doom Eternal since I have that game. On some maps in single player, the game will refuse to allow you to play on ultra nightmare settings because it needs around 6.5GB to 7GB VRAM, so you need an 8GB card even in 1080p in some maps. In Techspot review, they only play one map. They don't go through the entire game in the benchmark.
This issue was a similar issue in the past with the 3GB 1060 already not able to max games in 1080p. Games like GTA 5 would warn you that you were exceeding the VRAM limit. That was one of the reasons I decided to buy the 1070 for my desktop.