If they really wanted to, they could mount an ext4 fs as a single blob on disk directly into WSL. That won't really help if you want to run a GUI editor in windows against that identical directory though.
That looks awesome (thanks for sharing) but it seems to be a different thing? People are looking for a way to run existing Linux FUSE in SL, not develop new virtual file system implementations. They haven't responded to that request at all. https://wpdev.uservoice.com/forums/266908-command-prompt-con...