No it was quite different (again, unless they changed it? They might've, I'm long out of this scene). UWP apps had a lot more restrictions on them, the SDK was different, and you didn't have the full consoles hardware to use, compared to the "behind the NDA" SDK: it'd run slower, basically.
IIRC the homebrew you can run is mostly UWP stuff? But if you want to launch a _game_, built for an Xbox, it requires to be in the program.