To me, the "If it’s not thread-safe to do, then it won’t compile" part sounds rather more notable.

That's true of Haskell for the parallelism faculties. It's also true for STM. You can still get stuck or have race conditions with the other concurrency abstractions but it's less common than I encountered elsewhere. I didn't have problems resulting from mutable shared state that was aliased across threads and wasn't supposed to be, it's always explicit.