>I ... noticed that the last time it was updated was Monday, May 19, 2003 - does this mean that no submissions have been reviewed since this date?
No, there are many categories where the vast majority (99.9+%) of submittals don't belong. Such categories may be edited very regularly, but the only activity is rejecting hopeless sites and moving not-obviously-hopeless sites to more appropriate categories. There is no way for you to tell whether this is an orphan category or a mis-submittal magnet category, or some combination of the above.
For example, a submitter once reported that (a) his category hadn't been modified for two years, but (b) his site seemed to be hit by editors every two weeks or so. Obviously his category was a mis-submittal magnet, but his own site was neither obviously hopeless, obviously mis-submitted, nor obviously unique or needed. The regular editors regularly checked all the submittals, but didn't take on the thankless task of proving a probably-hopeless site was certainly-hopeless.