It is because this game is very CPU demanding. I wanted to know how the Xeon fares.
Xeon's are fantastic CPUs, newest and greatest doesn't always mean better. The only upside of non-Xeon CPUs is higher single core perf. And of course more modern features like on-cpu encoders, etc.
Anyway, to answer the OPs question, I just bought this game and maxed everything out on my machine and it is playing smoothly above 60 FPS at 4k all maxed out. Even enabled Ray Tracing all maxed out. Also this is a port of a PS5 game, so generally speaking, ports are not crazy intensive. There are far more complex AAA games out there that will push the 6900XT.
I also disabled FSR 2.0 (which is the newer gen of of FSR) and its still hitting above 60fps. When FSR 2.0 becomes main stream, high frame rates are not going to be an issue anymore. NVIDIA has had artifical scaling for a long time now, and AMDs is open source, so it will be more mainstream.
To sweeten the deal of the 7,1 Mac Pros, if the 7000 series GPUs are supported by Apple (hopefully) then it can extend the life of these machines for another generation.