It's worth noting that those numbers are partially because of licensing, not just technical constraints. All of the original publishing contracts allowed Micro

It's worth noting that those numbers are partially because of licensing, not just technical constraints. All of the original publishing contracts allowed Microsoft to sell Xbox/Xbox 360 games on those systems specifically, so Microsoft had to seek permission from each and every relevant third party publisher before making each title backwards compatible. From what I understand original Xbox compatibility on the 360 was similar, with 462/996 games ultimately being compatible "officially" (https://en.wikipedia.org/wiki/List_of_Xbox_games_compatible_with_Xbox_360 https://en.wikipedia.org/wiki/List_of_Xbox_games_compatible_...). But with a jailbroken system compatibility is actually a fair bit better (https://consolemods.org/wiki/Xbox_360:Original_Xbox_Games_Compatibility_List https://consolemods.org/wiki/Xbox_360:Original_Xbox_Games_Co...). Afaik there is no similar jailbreak for Xbox one/series, but if anyone ever does manage to get their internal emulator running with arbitrary titles I wouldn't be surprised if a lot more games work than their official numbers suggest.