Yes but the concrete types at the byte level can be used to say: "these five bits are, concretely, a type tag, and always a type tag", and so it goes from there

Yes but the concrete types at the byte level can be used to say: "these five bits are, concretely, a type tag, and always a type tag", and so it goes from there. I don't want to be typing at the high level the same way I'm typing at the byte level.