In our current bugzilla, there is only closed, not both 'resolved' and 'closed'.
Fixed the behaviour to close a bug when resolving instead of RESOLVED. As for RESOLVED being in the list of status to query against from query.cgi, this has been like this for some time. Not a regression.
There are currently 720 bugs with status "RESOLVED". Also, marking as a duplicate uses "RESOLVED DUPLICATE", not "CLOSED DUPLICATE".
P.S. Should all the bugs that existed prior to Bugzilla upgrade be changed to "everconfirmed=1"? Otherwise we'll have these weird occurrences of "UNCONFIRMED" status in reopened bugs, bugmail showing "everconfirmed" changing from 0 to 1 (for no good reason), etc.