I can appreciate all of the above, but it's stll anecdotal. It doesn't seem to make much sense that there is a stated limitation under the Emerald Club benefits as to who qualifies as a free additional driver, and then the standard contract ID for being an Emerald Club member that auto-populates for a reservation goes against those limitations. Terms below from Emerald Club page:

Authorized Drivers
Free (in the United States and Canada) - An Emerald Club member's spouse, immediate family member living with him/her, business partner, employer, or fellow associate who has an assigned corporate contract with National and drives the car for business purposes. All other additional authorized driver situations are subject to a daily charge. Click here for our policy on additional drivers.