An example that came up during converting the Lemmings Plus packs, in particular LPI and LPO, to the new formats was when I needed to add ceiling terrain, then needed to make the same change to a level's repeat version. I got around this ultimately by just copying/pasting in a text editor.
Similarly, this feature may be useful in general when dealing with modifications to levels that have/are repeats, or are otherwise similar (the "Code" levels from LPV was another such case).