By default, the paths in %PATH% in Windows 10 are converted to the
corresponding path under WSL and appended to $PATH. (Convenient, for example,
to start the Windows Explorer by explorer.exe in WSL.)

However, /etc/profile removes these converted path by setting 

PATH=/usr/local/bin:/usr/bin:/bin

There is a comment that the original value might be restored, but in fact the
variable to save $PATH is only unset later. 

But Microsoft documents at
https://docs.microsoft.com/en-us/windows/wsl/interop#run-windows-tools-from-wsl
on WSL all executables in %PATH% can be run by their full file name (that is,
including the exe extension). Thus openSUSE 15.1 behaves unexpectedly.


(This question was already posted in the openSUSE forum
(https://forums.opensuse.org/showthread.php/538192-WSL-OpenSUSE-15-1-converted-PATH-not-appended-to-PATH?p=2920113)
and on the reddit forum
(https://www.reddit.com/r/openSUSE/comments/dxos80/path_under_opensuse_151_wsl/).)

Instead of always disabling the appending of the converted %PATH% to $PATH, one
can opt to do so by adding

[interop]
appendWindowsPath = false

to /etc/wsl.conf.