I have not heard any sort of anything from developers about Geometry Engine being some sort of better than RDNA 2 front end change. Not a thing at all.
IIRC, the geometry engine rumors are coming from the same sources that leaked Radeon VII, Infinity Cache, clocks and a bunch of other AMD and Sony stuff well before anyone else and with very good accuracy.
If this was coming from rumor mongers with a poorer track record like e.g. AdoredTV I wouldn't be giving it much thought.
Incidentally, the same sources who described Sony's custom Geometry Engine also mentioned the PS5's CPU has unified L3 (which could be responsible for the better measured performance at very high framerates). I think he started mentioning these in his videos during the Summer.
So when a x-ray picture of the PS5 SoC comes out, if we see separate L3 for each 4-core CCX then I'll assume the Geometry Engine rumor is probably true. If not, then it's probably not true.
Are we really going for secret sauce again?
I have flashbacks from Xbox one launch.
You don't need to go back that far to find secret sauce theories.
The SeriesX launched 3 months ago, and when DigitalFoundry couldn't observe its predicted 15-20% performance advantage over the PS5 in multiplatform titles, we started hearing about how there's
a future devkit that will unlock the full power of the console.
Aside from Hitman 3 which for all we know it's the exception to the rule (and where we can't really compare both consoles because they're running different resolutions at over 60FPS), we're yet to see anything running better on the SeriesX in any measurably substantial way.
Regardless, I don't think anyone ever suggested the PS5 has unlocked geometry potential that will put it one step above the competition.
RGT's statements are simpy that the PS5's geometry engine is more advanced/flexible and the console's apparent lack of RDNA2's VRS stems from hardware design decisions taken around the geometry engine.
Note: I don't know how the console's geometry engine can influence the shading precision (and at first thought it doesn't even make a lot of sense), but then again I also haven't read Sony's multitude of patents around foveated rendering.