My VHDX mounted in a directory is affected by this, and actually broke a couple of tools until I also mounted it as a drive. (Using a VHDX helps bypass a lot of filesystem related perf impacts on Windows, so it's worth the occasional broken tool.)

I suspect (but haven't tested) that some file sharing handlers or attached devices could also hit it - thinking here of IoT devices that provide a filesystem-like interface.

Either way, I don't think the warning is spurious, and while it's not particularly helpful for people who pass in 8.3 names that are then expanded (it shouldn't ever happen the other way), that's easily fixed on the user's side. (And tempfile, which clearly needs fixing.)

I'm also *strongly against* warnings/errors that only occur based on a decision you made ages ago (or that someone else made for you), such as how you installed Python. Right now we have a warning that can be explained in exactly the same way on every platform and every circumstance, but Eryk's proposal/preference would suddenly make the case for the warning way too complex. Tutorials and teachers don't get to ignore it just because it only happens to some of their readers/students, and so we only make things worse for them by making it harder to understand. Better to have a simple, consistent message in this case.