That's not what I say, that's what the former PM Lead of WSL said. To be fair, Windows Services for UNIX was just Unix services for Windows. Probably the same logic applied there back then: they couldn't name it with a leading trademark (Unix), so they went with what was available.
WSA and WSL both coexisted for a time.
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.
That said, to address the grandparent comment’s point, it probably should be read as “Windows Subsystem for Linux (Applications)”.