Why do you think he wouldn't need to be added? Are you saying that you shouldn't pay the premium for a newly licensed driver to be covered under your policy. Think about it. Compare yourself to your son. You have years of driving experience (let's pretend that you have a good record). Who is more costly to insure? Do you expect the insurance company to "eat" the premium that they should earn for insuring a newly licensed, male, 16 year old, who thinks that he can't get a ticket (won't be caught) and can't cause a serious accident (because he's an awesome driver)?
Of course you have to add him to the policy to be covered. Also, its probably less of a risk if you DIDN'T have full coverage. That way if he totalled one of your vehicles, the insurance company wouldn't have a claim to pay.