Ocaml is notorious for having CLIs that use longform options with a single dash. It’s infuriating. So it would be -help in this example
Maybe, but I find it more likely that they just copied math notation. In mathematics (broadly, not just theoretical CS, also analysis), the type of something is indicated with an infix `:`, like `f : A -> B` is a function from A to B. This colon conventionally has equal spacing on both sides, like a regular infix operator.
There's the "Thing of int" weirdness also