The 6700 XT video looks good, but ICDP said it didn't have enough video memory to run 4K max settings as he's using one.
I can't speak to your 3080 TI, but there's plenty of videos up on YouTube showing them at close to maximum video memory capacity so I'm not sure what is happening with your setup.
Not too long after that screenshots was taken, FPS plummeted to single digits.
Both videos are in 1440p not 4K. 12GB of VRAM shouldn’t be a limitation at that resolution yet the 6700XT is using more VRAM than my 3080 Ti and is not stuttering. This indicates the game is not utilising the VRAM on Nvidia cards efficiently.
Regarding the 3080 Ti snapshot, that is allocated vram, not vram used per process. Allocated VRAM is around 11.5GB on my system at 4K but the VRAM usage without FSR never exceeds 10.2GB.
I will share a video showing my 3080 Ti using only 10GB of VRAM in the beach at the start of the game while the 3090 reaches 11.6GB. Both of them are stuttering, the 3090 less so.