IME, the best scenario is to create a generic admin user and use that to migrate a different user over. Once you have everything done, you can change that migrated user to an admin if you'd like and then get rid of the original account. Or keep that one for yourself.

Your run most likely did nothing because of the skip option.

While I've used the feature a number of times, it does have its quirks. Such as issues if the new user has exactly the same name as the one you're moving.