This is actually unrelated to UAC. The system will set the owner of objects created by admin/elevated tokens to the Administrators group; this prevents any non-elevated malware running as you from coming along later on and being able to modify the object (which it would be able to do if your user SID was set to the owner instead).
Since you're a member of the Administrators group, this is the behavior you'll get in the case with UAC turned off (since you're running as a full admin).
With UAC on, my suspicion is that you somehow ended up with Explorer running elevated (e.g., it died and you restarted it from an elevated instance of Task Manager, etc), and that's why you ended up with the unexpected ACL there.
Let me know if I'm reading the config or folder locations incorrectly, in which case I'll go back to the drawing board for the answer