It's not most libraries. They're rewriting very specific libraries in Rust, generally ones that require both memory safety and concurency

in fairness to them microsoft takes their backwards compatibility seriously to the point where i'd absolutely see them keeping their old implementation hidden somewhere and hot-swapping it in when they detect an old program that needs some inexplicable internal access to some C struct being launched.

Didn't know they did. And what I said was a jab at windowd but go off I guess you obviously want to feel hurt.