in all languages? i don't think so.

    def x = y where
      y = a * b
      a = 21
      b = x

Not really. E.g. there's no ordering in function composition that isn't also in high school math. Also, you shouldn't depend on e.g. maps processing elements in a given order.

My impression is that statement ordering is easier for mediocre but competent programmers than it is for excellent programmers. The reason is that writing correct imperative code is non-trivial, but writing correct-y imperative code is pretty easy. So someone who's carefully thinking things through while learning will have a more difficult time with simple assignments, because -- at least while learning -- they're essentially trying to construct the correctness proof in their head. And that's pretty hard for imperative code.