I don't believe this is correct. I have not once seen a new method being added to stdlib that causes code to not compile. And ABI concerns are a non-issue since Rust is statically linked.

It is correct. For example, this code (admittedly a contrived example, just to illustrate the point) compiles in 1.82 but not in 1.83:

  trait OptionExt {
      fn get_or_insert_default();
  }
  
  impl<T> OptionExt for Option<T> {
      fn get_or_insert_default() {}
  }
  
  fn main() {
      Option::<()>::get_or_insert_default();
  }

The reason is that `get_or_insert_default` was added to the stdlib in 1.83, and takes a different number of arguments, so it clashes with the user-defined one here.

Interesting, I would think that having OptionExt in scope would make it clear which method to use.