I really dislike that interpretation of the Kelly decision, and my own attorney would disagree a bit with it. This is specifically why I don't rely on NORML for up to date, accurate information, that's #1. #2 is wait til you speak with *your* attorney. The state laws do not actually limit anything, if you read the applicable sections that were affected by Prop. 215 and SB 420. Third, anyone who insists that the ID card protects you from arrest isn't living in the real world, I can guarantee you it does no such thing should the officers involved choose to ignore it.
Mine recommended against getting the SB420 ID card specifically because of the People vs Kelly ruling. IF you have the card, you are voluntarily limiting yourself to 6 OR 12 (mature OR immature). Because that aspect of SB 420 was indeed struck down, so for NORML to say that is, IMO, incorrect.
Your doctor's "prescription" has no real legal basis or grounding in law or the H&S or criminal or penal codes that were affected by Proposition 215 or Senate Bill 420. Just as there is no legal definition of a coop, collective, dispensary or other grey area outlets and growing scenarios. This, combined with another court decision the name of which I'm forgetting entirely right now are the reasons why counties like Fresno and cities and other local munis are able to infringe entirely on a patient's right to grow and remove it, criminalize it, make it a per se nuisance, etc.
Really, to fully understand what the law is, you have to read the law yourself. I would recommend having both a regular dictionary AND a law dictionary on hand, I use.. I think it's Blacks Law Dictionary, but Google Scholar can also be helpful, just remember to check the legal papers/decisions button.