You don't need dedicated hardware for CB, it just accelerates it.
Aside from CB, Insomniac games used temporal accumulation.
I think FSR 3.1 wasn't really the jump AMD was hyping. Makes sense that Sony is developing PSSR as a proprietary solution. Seems like AMD won't be able to deliver a viable DLSS competitor for a while.
AMD didn't hype FSR 3.1. They only promised improvements to image stability. And they delivered on that.
They never said it would beat DLSS or anything like that.
Ratchet and Clank, for whatever reason is the worst case scenario for FSR2.2 and even FSR3.1
But still, it was a significant improvement.
In games like Ghost of Tsushima and Horizon Forbidden West, the image quality is much better.
Like Ancient Gameplays showed, FSR 3.1 now is better than XeSS 1.3
Another thing to remember is that, the most likely reason why FSR2 never used ML, is because Sony decided not to have support for DP4A on the PS5.
AMD could not just leave one of their biggest costumers behind.
But, as soon as the Pro supports ML, both AMD and Sony say that their upscalers will also use ML.