I recall the 3090 8K marketing too. However, I also recall Nvidia talking about 8K in reference to the 4090:

https://www.nvidia.com/en-us/geforce/technologies/8k/

That said, I recall that the media was more enthusiastic about christening the 4090 as an 8K card than Nvidia was:

https://wccftech.com/rtx-4090-is-the-first-true-8k-gaming-gp...