You're right...
additionally, school letter services, where a packet of letters are sent, also covers their LOR requirements
here's what their FAQs states:
Q. What letters are required and are exemptions made on the required letters of recommendation? My physics professor from last year is no longer with the university. Could I send in two recommendations from chemistry professors instead?
A. Generally JMC prefers a composite letter written on behalf of the applicant by the college or university's pre-health committee, if there is one.
Some schools do not provide this service but offer to collect individual letters of recommendation and mail them to the medical schools. If
individual letters are sent, we prefer one biology, one chemistry and one physics and one humanities. You may direct exemption requests to the Committee on Admissions using the optional information section on the Secondary Application.
Also, take a look at the Hard copy secondary app found here
http://www.jefferson.edu/jmc/admissions/appforms.cfm
on the pdf document, it states the following:
I. Letters of Recommendation: (Please read this section of the Information for Prospective Students brochure.)
The following type of recommendation letter (s) will be sent:
A. Health Professions Committee letters from College/University.
B. Recommendation Packet compiled by (Pre-Med) Advising Office
C. Individual Faculty letters (one letter from each required) 1-Biology, 1-Chemistry, 1-Physics, 1-Humanities)
this implies that if you use choice A or B, this strict requirement doesn't necessarily apply. I attended UCLA, which has a career center that compiles my letters....so i think i'm ok, but i might call them just to be on the safe side.