Isn't WSL2 just a VM?

Summary

"Subsystem" on Windows NT has a vague definition. It basically means an API set, but predominantly for supporting programs written for other operating systems mostly through lightweight call translations. Windows NT, formerly "NT OS/2", used to have an OS/2 subsystem that supported running OS/2 applications just by translating API calls to NT. Subsystems usually have a separate process for state bookkeeping. There used to be an OS/2 subsystem (OS2SS.EXE), but there were more. Even Windows is a subsystem on NT architecture. The enigmatic CSRSS.EXE is the Win32 API translation layer for Windows NT. You can see the pattern: the "SS" stands for "subsystem". Because of its performance problems, some portions of CSRSS were ported to kernel mode and were called WIN32K.SYS. There was also a long-lived, pretty much useless POSIX subsystem (PSXSS.EXE) on NT. It was mostly to sell NT to the government because they required operating systems to be at least POSIX.1 certified. It implemented the bare minimum POSIX API to get the certification, and nothing else.POSIX subsystem was later replaced by a more complete Windows Services for Unix developed by Interix, based on OpenBSD API. Unlike other subsystems, it was not binary compatible with any Unix, but provided its own API set and tooling, so apps could be compiled for it.Enter WSL1WSL1 is the first incarnation of Windows Subsystem for Linux. I think the name is silly though because we all know that the actual Windows subsystem for Linux is Wine. I wish Microsoft had kept its initial name: LXSS. Anyway, WSL1 is a thin translation layer like the subsystems I mentioned. When you run bash on WSL1, it only allocates a few MBs of memory just what bash needs, and that's it. You could see and manage bash process in Task Manager along with other Windows processes:Linux bash showing up next to ASUS bloatware on Windows 11This is the full process list that shows up on top:Okay. bash allocates only how much it would allocate on a Linux mac...