There's also the fact that *Cygwin's* Python will behave like a *nix Python
and use backslashes. It's only the Windows Python that follows Windows
platform conventions.

So there's already a reasonable workaround in the cygwin case: use the
version which relies on the POSIX compatibility layer, not the Windows
native one.

As David pointed out, unless/until someone that is affected by the issue
can come up with a coherent design proposal for what the behaviour *should*
be that is a better solution than "just use the Cygwin Python instead if
you actually want POSIX behaviour", this isn't going to progress.