Re-created user has all material from old user with same username?

If I delete username foo from ownCloud 9.1.1, then create a new username foo, then the new username foo can see all the things the old username foo had. Is this by design?

How can I force ownCloud to cmpletely delete the user account?

Did you wait a bit that at least a clean up routine from the cronjob can be carried out? When you do delete a user, you normally have a few seconds to undo this action. There is a known bug with calendars though (https://github.com/owncloud/core/issues/25912).

Thanks, @tflidd, I see that issue also has a commit to delete address books on user deletion. Looks like this is fixed for 9.2.