I think I kind of know what the author was getting at, but I'm not sure, and ending with the moral equivalent of "If you disagree with me, I guess you're just stupid" was a bit disappointing.

I think the idea is the potential problems with this could emerge if you have two people simultaneously doing somewhat larger complicated merges that have this core problem perhaps more than once. I think that may be true, but the probability of this occurring is well below just plain-old-fashioned human screwups, and the solution to both ("laborious history comparison, examination, and a reset --hard to a hash by somebody") is the same in both. I really don't see how fixing this would solve any real-world problem.