That quote by the author says 'I expect this behavior'. It does not give some use-case that would rely on it, aside from the use case of 'I use git, and incorrectly assume that merges are transitive.'

More specifically, if they pulled the same patches, the outcome would be identical. What he wants to be able to do is pull the same history by pulling different patches in that history. A patch is the diff between two repository states, and that's all it is. Sadly, diffs are intransitive.