There needs to be some trust between the builder and the glazier. If the builder makes the hole slightly out and the door won’t fit, the glazier would take the financial hit.

You should be able to find a builder who will do the complete job, you don’t really need to get a glazier to fit a door and frame. However if you want a particular door that you can only get from this glazier then you could get the builder to cut the hole, make good and then temporarily board the opening to make it secure.