This is simply false. Windows APIs are stable. It's one of the best platforms for back compatibility. The kernel32/user32 API has been stable for 20 years. Rust has some work to do.
That’s exactly my point: The problem is that Rust doesn’t use the stable kernel32/user32 functions (VirtualAlloc etc.), but the libc ones, which don’t have a stable location on Windows. Without looking it up: Which DLL do you have to redistribute this week to get “malloc”?