Windows just localizes how it shown on Explorer (and have API to get localized name), so real path is still C:\Users\user\Documents . macOS does the same thing by the way as you wrote. I don't think it's a problem.

Only XDG based systems use real /home/user/ドキュメント (in Japanese) directory . This is annoying. Please localize it well as Win/mac does.

Now yes, but it didn't used to be that way. No, I can't tell you which version changed that, it might have been 2000. :P

Right, I still remember programs blowing up because they expected C:\Program Files and then encountered C:\Programme - that one at least got better when WoW64 forced the issue for english-speaking devs.

I 100% agree. Localized directories was a stupid mistake. The way Windows does it today is much better and XDG should follow suit.