Why is it called Linux, though? There's no Linux there at all IIRC, in the sense that it's not using the Linux kernel.
It's not. It is called the Windows Subsystem for Linux. As I pointed out at https://news.ycombinator.com/item?id=11417059 and elsewhere, this name is in line with similar names that go back a quarter of a century, and they are all in one way or another named after the part that the Windows NT kernel substitutes for.