That's nonsensical suggestion.
The only reason PS4 Pro was possible for Sony was because they waited 3 years after 28nm went out of style and used 16nm fabrication. It will be impossible for Sonyto ever pack a machine worth a "Pro" moniker on top of PS5, when the base PS5 will already be using the state of the art nanometer process to get as high as the transistors will allow.
They will never intentionally low ball what they can do with PS5 and withhold people from coming on board just to charge for a simultaneous launch with a more powerful box at a higher price and a higher cost to themselves.
It is possible, with the Pro they pretty much know there is a market for a more premium version, 1/5 isn't bad by any means.
Margin is also probably higher and AMD would definitely want to sell parts they also make more money on.
Just like the shift from 28nm to 16nm happen there will be another switch 7 > 5 within PS5's lifetime, which would be under the 3 years of PS5's launch.
Along with that AMD's new GPU (the one after Navi) will also be out by then, so you'll end up with the exact situation that happen with PS4 / Pro.
It is a smaller shrink but it is one nonetheless and if it's viable then what's to stop Sony from releasing another refresh to cater that market.
One could even argue that 7>5nm won't be worth the wait and they could launch 2 SKU's from the get go and get as many to buy the more expensive model instead of missing out on 3 years of sale.
I'll tell you one thing though those hardcore players that want more power in a console ain't going to be content with 10TF, I as hell ain't.