The documentation does say this clears duplicates in Default Group. See my original post; they're not in Default Group. If you're not aware of this, if imported AD includes user OUs, and users in those OUs log on to an affected computer, User objects appear in SEPM in the User OU instead of appearing as duplicate Computer objects in Default Group. The script does not handle these.
Tried the script anyway on your recommendation and bumped SEPM for good luck. Didn't work: They're still there.