The problem with your assumption that "pcs will have the same speed or more" is that only 1% of the PCs will have that same speed, while all PS5s will. So games for PC will probably not run that well for a long time unless game engines are optimised for the 1% (which can happen, but will take a while). Even today you have computers being sold with disk drives, so yeah, not marketing, but I'm sure PS5 and Xbox having fast SSDs will push PCs to catch up.
But my second point is:
The graphics card mentioned goes for around 500 - 600$. An SSD comparable with the PS5s will be at least 200$ more. You'll probably be able to buy 2 PS5s juts for the price of these components on the PC, not even counting with RAM, motherboard and whatever ticks your gaming fancy. After you're finished, wouldn't be surprised the equivalent PC being 3 times as expensive as the console (that will most likely be subsidised by Sony).
The demo is awesome, and I'm sure anyone will be able to build a device with the same specs as the PS5 eventually (even though there is a lot of magic in the tighter integration of RAM with the SSD that is nowhere that I have see on the PC side), but it will cost a LOT more, and that has been the point of this, since the beginning. Affordable gaming for people that don't want to tinker and play with their parts. There is something really awesome in getting home from work and resuming my game from my sleeping console from exactly where I was 100% of the time.