Im having the same issue, however i HAVE enabled it with the reg fix.

Below is the storage settings, only showing C: , "New apps will save to:" dropdown is activated, only showing C:

This is my storage as windows sees it:

When i try to download and install a game from Windows Store i run into problems because i dont want this game on C: or D: , i want it on G:

Lastly the registry settings:

Anyone able to tell me how i can get my other drives to show up in Storage, maybe this will fix the issue?