Good point. I will just confirm that this is the case and that we'll work on this.
I also use Emacs under WSL, so we want this to work well.
It is implemented via directory-abbrev-alist so if you remove the entry from there
after Hyperbole is loaded, it should be disabled.
The idea was two-fold:
1. I believe WSL is moving to using /c instead of /mnt/c for simpler paths.
2. If you use something like Git Bash on Windows, it uses /c rather than /mnt/c,
so doing so in Emacs would be consistent.
But of course the /c link to /mnt/c needs to exist for this to work properly.
Personally, I created that link manually and will have to look at Microsoft is doing
about this in both WSL 1 and 2.