I’m assuming they mean that Swift generally is easier to use with dynamic types than Rust. Rust has dynamic polymorphism like Swift, but Swift you opt-out with

I’m assuming they mean that Swift generally is easier to use with dynamic types than Rust. Rust has dynamic polymorphism like Swift, but Swift you opt-out with final (correct me please if I’m wrong here), whereas in Rust you need to promote to a trait object. This is a small difference, but means you’re starting with different principles available to you out of the box. Personally I prefer Rust’s opt-in to complexity model, but I can see why people see that as a hinderence, even if it’s technically just as possible to do in Rust.