GUI needs a notification when run without --auto-dev-updates that subvolumes may not be populated.

[croogrog]

The lack of subvolumes populating as expected and the lack of explaining why is misleading to the user.

Even better than just a notification would be to allow the effects of --auto-dev-updates to be accessed In the gui.

In my opinion for a tool that does destructive operations (like formatting a drive or partition) to not populate something like btrfs subvolumes because "it requires potentially dangerous operation like mounting or filesystem check" is absurd. Most of us mount and unmount partitions daily with no issues. And in my experience filesystem checks have been at worst useless.