That is an interesting view. What you said about the extra mental step is true for me when I read the common "X x" notation, which is astonishing because I saw it vastly more often than "x: X". The later reads very naturally for me and I suspect that at least for my brain it is close to how the colon is used in natural language. Often you have a proposition and what follows after the colon adds detail to proposition or describes it in more detail - exactly like a type is additional information about the thing to its left.