Even we faced this issue when migrating from 5.6.1 to 6.1. The problem here is that your package has all users (at folder level - alphabets, numbers, etc), so what happens is it will replace the existing the folder structure which will remove the existing users including admin and anonymous which are now created with random id.
You'll want to double check your particular instance, but on every instance I've worked with past 6.0 the admin user shows up in a different place. So for your specific error, it looks like you excluded the admin user in the source instance, but it's trying to overwrite it on the destination instance. Find the admin user on the new instance, and add that path to the exclusions too - that might help. I would suggest excluding the 'system' user folder too, since 6.0 and 6.2 have lots of changes between the two. Basically exclude anything that might have been included by default on either the 6.0 or the 6.2 instance.
I usually put all users in specific folders (not the default folders), for instance all LDAP user accounts are created in an LDAP folder, any local accounts for specific projects are in a project-specific folder. That makes user migration a bit more simple.
A final note - I've had users with authentication issues unless you exclude the .tokens node under their user account. You can do a wildcard in the path to help with that.