It was called Project Astoria previously. Microsoft releasing the Windows Subsystem for Android for Windows 11 is news to me. I thought that they had killed that in 2016.
Anyway, Astoria was an internal product which management ultimately killed, and some of the technology behind it later became WSL and much later, WSA. WSA's inital supported OS was Windows 11.
Microsoft being Microsoft, they artificially handicapped WSA at the outset by limiting the Android apps it could run to the Amazon App Store, because that's obviously the most popular Android app store where most apps are published. [rolls eyes] I don't think sideloading was possible. [rolls eyes again]
I don't work for Microsoft and I never have; I learned all of this from watching Windows Weekly back when it was happening, and from a few videos by Dave Plummer on YouTube.