>> It happens when you deduplicate code which isn’t an exact duplicate, but only appears to be.
Embarrassing to admit, but until now I didn't think in this perspective - and on hindsight it should be obvious, sometimes code might look duplicate, but is not
Or worse, the natural progression should be that they diverge, but because they now share some kind of "reused" code in a library or class, an abomination is added to one or both users, just to keep the original "shared" feature.