Very confusing but very interesting. I'm trying to follow as I'm the main maintainer of the rdiff-backup software, which goes cross-platforms, so these small differences might become important.

Now, looking into the docs, following your explanations, I noticed that https://docs.python.org/3/library/os.html#os.fsencode and https://docs.python.org/3/library/os.html#os.fsdecode state that the 'strict' error handler is used under Windows instead of the stated 'surrogatepass'. Again an issue with the documentation?

Also, the 2nd paragraph of https://docs.python.org/3.8/library/os.html#file-names-command-line-arguments-and-environment-variables speaks only of surrogateescape and doesn't make the difference between POSIX and Windows.

Very interesting but very confusing...