Yes, I just tested it and it works:
To get the creator, role, or username of the user backup the tip is to look at this file:
backup\user.conf and look at the variable values like this:
username=myuser # (the username)
usertype=user # (can be reseller, admin)
creator=reseller88 # (who created this user)
I think this works perfectly as the user backup in admin_backup tool section just uses the copy of the user_backup method. They are identical files (I have verified this with winmerge tool).
@smtalk can verify if this is true whether there would be no issue if we can use user_backup in admin_backup.
From my understanding.. when doing restoration for any users, the most important thing is the creator of the user backup must exist in the system first and the creator must have created a package for the user if the backup contains domain. For example, looking at user.conf, the package is defined like this
package=USER_UNLIMITED
So, the creator must create a package with this name first. So, first choice 1) you either create a user and restore the backup on the existing user in the user backup tool section or second choice 2) if you want to restore using admin_backup tool then you have to make sure the backup has a proper name using the syntax above and with a few conditions like above (using this way you don't have to create a user first) but you must restore it using admin. The OP saw the error because DA restore did not detect valid file syntax for the admin_backup.
Also I think we can also use admin_backup file in user_backup section.