Patrick Steinhardt [off-list ref] writes:

Yeah, agreed. I think that the reflog is insufficient for a lot of Git's
operations and that it is way too hard to reason about.

As the reflog has never been about undoing, this is understandable.

Things like @{-N} notation and "git push --force-if-includes" make
good use of the "what was this ref pointing at historically?"
information, so they give us a proof that it is possible to
programmatically go back and find the necessary state, though.