Open With not working for scripts

When I "open with" a shell script with Bash, I get this error message:

/bin/bash: D:\Path\To\Scripts\dostuff.sh: No such file or directory

Which is understandable, because Linux uses a different way to indicate paths.

Expected results

I'd expect it (not sure what "it" would be) to convert the supplied path to a path that is usable for bash, e.g.
D:\Path\To\Scripts\dostuff.sh -> /mnt/d/Path/To/Scripts/dostuff.sh

Steps to repro

1. Make sure you've got a shell script (a .sh file). Any will do.
2. Right click -> Open With -> Choose another app
3. More apps -> scroll down -> Look for another app on this pc
4. Type C:\Windows\system32\bash.exe (or whereever your Windows install is, you know the drill)

Now Bash will open very briefly with the above error message. Steps 2 to 4 can now be replaced with a simple doubleclick on a shell script, still resulting in the same error message.

Windows 10.0.14393 x64

Reproduce the issue through the reported Open With flow using C:\Windows\system32\bash.exe and a .sh file, then inspect the launcher entry point that passes the Windows path to Bash. Done means the script opens successfully with a usable WSL path such as /mnt/d/Path/To/Scripts/dostuff.sh; no repository file or test is named, so locating the implementation and coverage requires project research.