The entire "idea" of Rust is the ability to achieve memory safety by mutation XOR multiple references, which is a different way to achieve the benefits of referential transparency/immutable data structures without the loss of performance.
Rust is not a "functional language" in that sense, but that was not the claim made, which is that Rust is heavily influenced by FP. This is most clearly seen in the trait system (typeclasses) and iterator patterns.
Influence doesn't mean you're doing exactly the same thing. If I make a rock band influenced by classical music, that doesn't mean I'm doing classical music, but I'm still very obviously influenced by it.
Rust is not a "functional language" in that sense, but that was not the claim made, which is that Rust is heavily influenced by FP. This is most clearly seen in the trait system (typeclasses) and iterator patterns.
Influence doesn't mean you're doing exactly the same thing. If I make a rock band influenced by classical music, that doesn't mean I'm doing classical music, but I'm still very obviously influenced by it.