Good question, and no, it won't mess it up.
We override the default behavior of Gmod's check for groups.
Normally, Gmod would check if and only if player was an admin.
Anything else but superadmin or admin would be "false"
With ULib groups, the check also follows inheritance so therefore would work.
Following the logic in the previous summary, superadmin inherits realadmin inherits admin inherits operator
(and unstated, all groups inherit user)
Gmod would check "is player an admin?" ULib would answer, "well, he's a real admin, which inherits admin, so, yes, he's an admin"
The only drawback to this method, if you have other addons that check for admin access that you wouldn't want them to have, well, they would have it.
It probably wouldn't be difficult to find in the addon where the access check is, and change "admin" to "realadmin" (or whatever you name it)