I know it's been talked about, wasn't sure if it was official. Lots of rumours tend to get thrown around about new consoles.
I remember the days when the NX was rumoured to be the most powerful console ever.
The thing is with this, is that the PS4 and PS5 share the same x86 architecture, so backward compatibility should be basically inherent. It's like playing the same game on one PC, then upgrading your parts, and you just load it back up, but with better settings.