Except, as has been said in several places, it seems the 'dupe detection code' has bugs and faults (hard to believe, but some UO code is buggy and erratic. Imagine that...).
If they decided it was worth the loss of some paying customers who have legitimate items that are caught by that bug, and the loss of some paying customers who see what they thought were genuine items they paid for simply vanish overnight, then maybe they would go ahead with an automated deletion. My suspicion is that would be a huge mistake when we're already seeing low and falling player numbers, and simply not worthwhile.
What's in the game is in the game, for better or worse - stopping it being traded is sensible, and the results for 'innocent' people are inconvenient but not game-breaking. If they actually stop future duping, and/or act FAST to delete things when it is discovered, that is probably enough.