I don't think it's true that Rust is safer, using the terminology from the article. Both languages prevent you from doing things that will result in safety violations unless you start mucking with unsafe internals.

Rust absolutely does make it easier to write high-performance threaded code correctly, though. If your system depends on high amounts of concurrent mutation, Rust definitely makes it easier to write correct code.

On the other hand, a system like STM in Haskell can make it easier to write complex concurrency logic correctly in Haskell than Rust, but it can have very bad performance overhead and needs to be treated with extreme suspicion in performance-sensitive code. It's a huge win for simple expression of complex concurrency, but you have to pay for it somewhere. It can be used in ways where that overhead is acceptable, but you absolutely need to be suspicious in a way that's never a concern in Rust.