Exit 30, I'm a Dining CM and maybe I can shed some light on what happened when you called.
Yes, we do ask for the reservation # on every call, even if it's not booked through WDW. Honestly there is a "trick" to finding reservations that you can't locate under name/zip and I don't think this CM knew about it otherwise she would have found you. It would have been helpful if you had your reservation #, but you didn't as some people don't. Regardless, she still could have made your reservations.
I think her concern was if you are on the dining plan, she would not be able to attach that to your reservations. So if you were looking for CRT or Fantasmic packages which are prepaid, you would have to prepay and not be able to use your dining plan as a credit. So what I would have done if I couldn't locate you (which I'm sure I could ), Is create you in the system and make your reservations but advise you that the dining plan will not be attached to your res. Not a big deal unless you are booking CRT or Fantasmic. You can always advise at location.
The other issue would be if you were trying to book 90 + 10, we would not be able to do that without your reservation number. That is an absolute must.
For those of you who mentioned that you will just say you are not staying because you don't want to give out a bunch of numbers, we will see that you are staying anyways because we will need your name to check for you in our guest book. We check for everyone even locals, and we would most likely see your reservation. Really, it does make it easier if you have your number, the CM can pull up your reservation info and poof you're on your way.
I do apoligize that you feel you had a bad experience making your ADR's. This new system takes a bit to learn and as all systems there are little tricks that you learn as you go. Unfortunatly you did get a CM that was uninformed (or I should say informed but maybe not paying attention), which sadly happens from time to time. If you call back without your #, just ask them to check under your arrival day, last name and resort and they will be able to find you. If not, ask them to have a supervisor assist you because you know you are in the system since you do have a reservation #, you just don't have it with you. The only exception to this would be if you have a land/sea package.
I hope next time you call you get me!! I would be happy to help you make some ADR's.

Have a magical day!