Old user directory structure after upgrading to Elgg 1.7.2 not removed?

I've upgraded a test installation from Elgg 1.6.2 to Elgg 1.7.2. After calling upgrade.php all user directories were newly created in the new directory structure and their content moved.

But the old directory structure remained with the user directories completely empty. Is this as it should be or should the old user directories get removed by upgrade.php? Slightly unsure here... can I delete the old directories without causing trouble? After all they are empty.

The only directory that still had some content was most likely created by the identicon plugin in a g/r/o/u/p/group:GID tree. It seems the identicon plugin saved the created group icons in these folders. After upgrading to Elgg 1.7.2 the identicon plugin has a new folder called identicon in the root of the data directory. The group icons are now also in this directory.

Could it be that the old directory structure was not deleted just because the folders created by the identicon plugin doesn't belong to a user and therefore is not manageable by upgrade.php?