when a bug is resolved (rawhide, current, errata) there is no more information as which package version has the fix into, so that it can be successfully matched with later package versions. this won't be as bad if when a release is rolled, all the resolved bugs won't be rolled to, and as a result the number of bugs on a packages is always growing making it harder to look for possible duplicates.
Red Hat's current Bugzilla version is 2.18. I am moving all older open bugs to this version. Any bugs against the older versions will need to be verified that they are still bugs. This will help me also to sort them better.
There is a fixed in field specifically for this purpose if the closer decides to use it.