I am curious about this as well.

The way it's phrased it makes me understand a bit that it could be used within FFI, like if you get a pointer from a extern function that returns a *mut T, I could have better semantics by wrapping it with Pin<&mut T>, but then it says

"Another fact about the pinned typestate is that for most types it is completely irrelevant. If the value of type can never contain any self-references, pinning it is useless"

Mind you I'm very new at FFI but I'd like to understand what are the best ways to wrap them into safe Rust.