This is a good example of gen-on-gen improvements in CPU/GPU architecture and good optimization on the developers part.
Last gen barely manages 1080p/60 with drops and next gen is mostly 2160p with no drops.
TBH I am not sure that is the case. If we look at any other game SX and PS5 are just about 2x more powerful than previous gen X and some 4x more than the previous gen base consoles. I do not think this game is CPU heavy it is a cross gen game, something like CP2077 and others are more demanding and proper representative.