Which have very sparse documentation, but do work just fine.

Win32 covers a lot more than xlib, athena and motif. And still I have to resort to porting over bits and pieces from the FreeBSD C library because in a pure win32 project (no msvcrt), things are missing.

The thing is, getting all the details right requires extensive research and a lot of extra nonsense that shouldn't be necessary. For compatibility, accessibility, consistency, etc. Sometimes it's amazing things work at all.