Sort of, this API enables static dispatch, but it could also have been written as

   pub fn read<P: AsRef<Path>>(path: &dyn P) -> Result<Vec<u8>>

In which case the size of `path` is always the same(two words[0]) and the same machine code could be used regardless of how the function is called. Rust still cares about the memory layout but because `&dyn AsRef<Path>` has the same layout for all implementations of `AsRef<Path>` there's no need for monomorphization[1].

0: https://doc.rust-lang.org/1.80.1/reference/types/trait-objec...

1: https://rustc-dev-guide.rust-lang.org/backend/monomorph.html...