Clock upgrade helped to stabilize 30fps on last gen consoles, no one was aiming for 60fps back then. So if GTA6 is dropping to ~45FPS on Zen 2 in Pro, 4.2GHz clock upgrade could bring that performance up... But Sony was too afraid to raise power limit of the APU for some reason.
We also, for some weird reason don't have open world, city based games this gen (and even last gen) - even with massive CPU upgrade compared to PS4. Almost all open world games are set in the wild (something
SlimySnake
mentioned when talking about that car UE5 game). So there is nothing to compare GTA with...