Of course I don't know what Rockstar, and Sony, are aiming for here. Hell, I even just talked about a possible scenario were "60 fps on Pro only" could happen.
But I see no reason why they would really act that way. It would be rather...odd behavior. Based on 40+ years of following the gaming industry (with less gaming than I would like, at least for the last 20 years)
Btw, you can't just refer to "optimizations". That implies that its a technical question. It really isn't, it's more about design choices and strategies.
Edit: If Base/X/Pro get a 60 fps mode I think you will get what you wish for anyway. The Base/X versions will probably look rather rough/low-res. PSSR (updated with FSR4-like quality) will greatly improve the overall presentation putting the Pro-version well above the Poor versions... And better less noisy RT on top of that. So in a sense the Pro is an "60 fps but not rough"-enabler.

I'm however worried that Rockstar won't put enough effort into the Pro version, let's hope they have some kind of deal in place, like you talked about.