> But this is true for ML syntax too, isn't it?

In ML, function application is left-associative, and therefore `a b c` always means `(a b) c`. It can’t mean `a (b c)`, even if that would fit the types.

The expression structure is therefore independent from the types in ML. You can parse the expression tree without a symbol table. In concatenative languages, on the other hand, you need to look up the types, or if the language is dynamically typed, the expression structure only manifests at runtime.