Not meaning to get into semantics, or indeed to appear pedantic, but for me if an obverse or reverse die were not meant to be paired together, then subsequently saying it was an intentional action is somewhat contradictory, since at that point they clearly were meant to be paired together, as the intention at that point was to do so.
It may not have previously been the intention, but once it is accepted, even as a short term expedient, then they are clearly meant to be paired together. So in my humble opinion, the 1926 ME is not a mule. The 1860 beaded/toothed border is a mule, as this was much more likely to be a production error.