During my interview, my interviewer explained to me a little bit about the UC San Diego admissions process and how candidates are selected for an interview. He explained that there is a scoring system, which basically awards points for your activities/awards/honors/experiences that you discuss in your AMCAS application (namely, the personal statement) and autobiography. (I think UC San Diego actually substituted the AMCAS application entireley with the UC application.) I'm sure your grades, MCAT score, and letters of recommendation also fit into the scoring system, but my interviewer did not explicitly mention these categories.
With the above said, I'm sure a scoring system is also put into place for the interviews. I speculate, then, the interview scores are combined (by some mathematical formula) with the score that was used to identify who received interviews. Finally, the overall score is used to help the Admissions Committee decide on a final decision for a particular applicant. For those in the "Acceptable Pool," I'm sure the scores of all the applicants helps to decide who gets ranked where in the waitlist. I just could not imagine the Admissions Committee reviewing all the 300 applicants in the "Acceptable Pool" again, but I may be very wrong. I am just trying to provide a rationale for the UCSD admissions process and figure out why Jefe, perhaps, was told where he lies in the "Acceptable Pool." I guess this is just my two cents.
By the way, Jefe, are you sure she said you were in the bottom of the "Acceptable Pool"? I just could not imagine the person on the phone telling you this information, which I hope she did very politely. However, maybe you misheard the person. He/she may have been referring to the location of your application folder within a stack of folders as she was pulling it out to look at. Sorry, Jefe, another crazy hypothesis by me!
Good luck and don't give up just yet.