The problem with WSL1 was the very different file system semantics between Windows and Linux. On Linux files are dumb and cheap. On Windows files are smarter and more expensive. Mapping Linux file system calls on Windows worked fine but you couldn't avoid paying for that difference when it came up.

You can't resolve that issue while mapping everything to Windows system calls. If you're not going to map to Windows system calls then you might as well virtualize the whole thing.