Wine is a lot broader in scope than WSL, while Microsoft is fine with implementing a kernel-level ABI and then shipping a download for an Ubuntu userspace, Wine cannot ship any official Windows components. They had to re-implement every important DLL from scratch in addition to the ABI.

I can see why you would think that, but there is a reason that many think the opposite. Wine is obviously less compatible than WSL, but it is also a much more ambitious project. For WSL to work, it "only" has to implement the kernel translation layer and then run the various userspace tools that Linux does (GNU tools, Gnome, etc).

For Wine to implement even enough to run Notepad, Wine needs a reimplementation of huge portions of userspace. Of course, this also means it is a little bit of an Apples to Oranges comparison.