I did do the math, that's how I came to this conclusion. I believe it's like 2500 Xbox One games, 600 Xbox 360 games, and 39 Xbox games. The total came out to 3197 games backwards compatible on Xbox Series X, vs the PS5's reported "4000+", as has been cited by multiple sources.
As for the bolded...yeah man, this is gonna feel good. in this house, neither of us have the PS4 pro, but we both have PS4s (My launch model and her slim model), so all the PS4 games we DO have will either be upgraded to utilize 4K or get an upgrade to a PS5 version.
Here's the hilarious part where I remind everyone Sony had 6 different catalogs to pull from to MS's three.