Yes, there is a separate filesystem for WSL, but you can still traverse the Windows filesystem as well, including mounting external drives. You can also browse the linux filesystem from windows explorer as expectded.

https://docs.microsoft.com/en-us/windows/wsl/compare-version...

https://devblogs.microsoft.com/commandline/access-linux-file...

https://community.openbiox.org/d/72-windows-subsystem-for-li...