Generally, you wouldn't type out the spec either, either you provide an existing spec to the model (in form of white board notes, meeting notes, etc.) or you iterate conversationally until you arrive at an initial implementation plan.
It's a different way of working for sure, and it has distinct draw backs and requires different mental modes depending if you're doing green field, demo/prototype, existing large app feature development etc. but it's been a massive productivity enhancement, especially when tackling multiple projects in quick succession.
