PS5 GDC Reveal and PS5 specs/performance Digital Foundry Video analysis : 3.5 Ghz 8 core Zen 2 CPU along with 10.3 TF RDNA 2 RT capable and 16GB GDDR6 RAM and also super crazy fast 5.5 GB/Second S

[DonFerrari]

Hiku said:

DonFerrari said:

Just a small correction, MS had some features backed into the X1 that made their BC possible, it was on their plan since they designed the console.

Do you remember where you read that? Because in an interview I remember he said he was surprised when they figured it out, which happened years later.
Not the same interview, but here's him saying "While we weren't sure it was possible..." https://youtu.be/HDhh8jy1YQI?t=27

In that same interview I recall that some engineer/s asked him if they could work on this BC project, and he said ok. So that sounds like it wasn't planned from the start.

“We had to bake some of the backwards compatibility support into the [Xbox One] silicon.” Considering the first back-compat 360 games didn’t hit Xbox One until 2015, that’s mightily impressive foresight. 

https://www.gamesradar.com/how-xbox-one-x-emulation-technology-is-helping-to-resurrect-the-last-two-generations-of-xbox-classics-in-4k/

Perhaps he was surprised at how well they made it or perhaps there is some misleading between the baked in being specifically for BC or something they were able to make use. (Like when I said the 3D audio chip in PS5 working like SPE then perhaps it could be used to BS PS3).