It was an historical reason. WSL1 was named such because instead of using Linux kernel, Microsoft uses Windows NT subsystem to run Linux userland (hence Windows Subsystem for Linux). As WSL become a well known name, the next iteration (the one with the real Linux kernel) is simply named as WSL2.

Subsystem here is a reference to a Windows subsystem. There are many subsystems within Windows that handle various OS functions. In this case, a subsystem was created to handle running Linux.

It's phrased in a very confusing way, so it's a very poor choice of names, but I wouldn't go so far as saying incorrect.

The preposition "for" has a lot of different meanings, and the one they've used, though extremely unexpected here, is legal.

They mean it in the sense that it enables something, like in "tips for success" or "a budget for entertainment". This is a Windows subsystem, and what it's for is making Linux stuff available as a feature.

In the context of computers, "for" commonly means targeting toward or being compatible with something, like "apps for iPhone". Which is not how they mean it. And which is why they should have chosen something different.

I'm waiting for the Datacenter Enterprise Pro Plus version.

Windows if full of weird names for it's subsystems if you look closely.

The old installer had "Windows Executive" and "Human Interface Parser" as installation items that always had my head scratching

It's the Windows Subsystem for (running) Linux.

It wholeheartedly agree with you, yet I suspect Microsoft would never name a product of theirs "Linux" first and "Windows" second.

On the other hand, they named their 32-bit Windows emulator "WOW64 (Windows-on-Windows 64-bit).

It's neither these days. It's a glorified VM.