With how underpowered the CPU for the PS5 is, it doesn't matter how strong the GPU is.
It will be equal to an undervolted 4070 to keep heat in check.
After that, sure you get more performance than a base PS5 and a RX 6700 xt / rtx 3070 but a 4070 will still clear the PS5 by a bit.
And at that point, with how much a PC can do... You can't really justify upgrading if you already have something similar + a base PS5.
I'm starting to believe that the PS5 pro is a marketing tactic by Sony, they put such an outrageous price on the thing so you look at the Base PS5 and say "Damn, this is the better deal".