There are no rules from AMCAS that says what activities you "must" have an MME on. Individual schools may express a preference (they should be upfront about that). However, you have many other opportunities to talk about your clinical experiences throughout the secondary essays and interviews so don't get too worked up about this detail.
Most advice to applicants focuses on the personal statement and description of work or activities required to complete the initial centralized application
www.studentdoctor.net
This type of advice by rumor is likely the same source that says you must have a doctor letter among your LOE's.
Adding: I would hope your 3000 hours as a student-athlete would be meaningful to you, and to me, it would look weird if you didn't comment on it somehow. But I also acknowledge, it's your application. You gotta do you.