If you remove gc from ocaml, and added in compensating alternatives it would end up looking something like rust.
I think a lot of the adversting around rust in a "better c++" but its actually ocaml like but not mentioned to avoid scaring away traditional systems devs.
For example, everything should be a reference by default, and use of explicit & is stylistically bad.
Or why in let mut iter = a.iter(); iter is mut? It should be a simple closure which follows a protocol. In what sense it is mutable?
And such small warts are literally everywhere, together resulting in a clutter.
A functional language uniform defaults (everything is an expression, everything is a binding which implies everything s reference) are much better.
Second, what you said is true, but also not really relevant; mutability is part of the API in Rust, and so that is part of the interface.
To make it more concrete, https://doc.rust-lang.org/stable/std/iter/trait.Iterator.htm..., the protocol, takes &mut self. So it must be mutable. It's following the principle you're talking about.