I think certain people claiming its unoptimized on PS5 haven't actually played the game. As I said you have incredibly detailed environments with a huge draw distance and then you have hundreds of thousands of rats within them.
Obviously everything can be improved but we are at last starting to see what these new consoles can do, and there's a lot more to come.
The CPUs in PS5 and Xbox Series are fundamentally the same. Same architecture, same core and thread count, same support for various instructions including AVX 256. There may or may not have been a reduction in PS5's CPU's FPU, don't know if that was ever clarified or if it did, got redacted afterwards.
The only other real difference are the clocks but assuming the game is using SMT, that difference is no higher than 100 MHz in Series' favor. That would not be enough to cause the difference in performance with the rats (assuming all of that logic is CPU-bound, which it likely is if Series S has similar rat counts but performs those sections better than PS5) when the MHz difference is so small.
It COULD be the dynamic resolution on PS5 in those sections is maybe too high when accounting for all the other stuff going on, but I dunno what the resolution for PS5 is in those sections compared to Series X (I'd assume Series X is slightly higher resolution for those portions). I simply fail to buy the idea that PS5's CPU isn't up to the task for the rat simulations considering it's virtually the same as the Series' CPUs, just 100 MHz lower.
Even considering it's a GPU issue, that again would be down to lack of some specific optimizations. Theoretically PS5 could be seeing upwards a 2% GPU perf drop providing more power to the CPU, but that would reduce the MHz difference CPU-wise to something even smaller, and the GPU would still be performing at slightly over 10 TF.
So it's definitely something related to lack of specific optimizations in the PS5 build, and that might be due to Asobo leading with the DX12 Ultimate APIs because that's what the GDK uses and it makes Xbox & PC (Windows) simultaneous development effectively seamless.