I'm not be sarcastic or funny when I ask this. Why isn't this called the Linux subsystem for Windows? It seems like a Linux subsystem running on Windows. If it were the other way around, (ie, a Windows Subsystem for Linux) I'd think that Linux would be the primary OS, and something like WINE would the subsystem.
I think it's supposed to be read as "the Windows subsystem for [running] Linux [applications]". Back in the old days there used be a thing called Services For UNIX (SFU), which was a bunch of Windows tools and services that provided UNIX-like behavior. Then came Subsystem for UNIX Applications (SUA). And now it's WSL.