You have two repos with different history:
master -> patch a -> patch b
master -> patch b -> patch a
But the contents of the files are equal after applying both patches (in either order).
Git will consider these to be two different, Pijul thinks they're the same.
This is a simplified example. It only gets interesting when there are a lot of patches, some of which are commutative and some are not.
If the VCS knows about dependencies between patches intuitively, it could free me from having to explain it, which in the case of Git, requires following procedures that I'm unlikely to convince any of my coworkers to follow ("ohay, first, decide on the earliest point in the history from which this patch could make sense, rebase onto that....")
You and I, who are both working off of main, and who have both separate merged in a few patchsets that are relevant to our shared module of interest. We can merge and compare our branches, and the differences in terms of nursing patches without having to be rigorous about reconciling or histories.