This is true to some extent although the point I was trying to make was that that an SSD could have an influence on the game design and streaming in the first place, which seems strange yes but a lot of people at the time of the PS5's release denied that an SSD or any form of high bandwidth low latency storage solution should effect games. The infamous "it can run on my rig with a HDD just fine".
As for Cerny's "overkill" solution, I believe it's his job as an engineer of the consoles to make the right bets and take risks, the PS5's SSD was one of those and that vision has not "yet" been fully realised, or it may never, we'll see.
Regardless I'd say the PS5 is an extremely well designed console, and offers performance parity with it's competitor the Series X despite the latter's advantage in compute performance.