Answer: Denial, plain and simple.
Definition: Denial is a defense mechanism in which a person is faced with a fact that is too painful to accept and rejects it instead.
If you're black applicant admitted to DePaul with a 149 LSAT when not a single white applicant was admitted with anything below a 156, you'd also hesitate to list your LSAT score. You've been admitted solely based on your race but you'd rather have others, and yourself, believe that it was based on merit, so you enter into denial. In fact, you weren't smart enough and didn't deserve to be admitted - a very painful truth that psychologically, if accepted, would drive one to withdraw. There are thousands of black and other URM applicants out there dealing with this issue right now, and not listing an LSAT score or listing a false score are symptoms. How painful it must be years later, after graduation, to have your peers and society as a whole assume that you were admitted to law school and hired by your current firm simply because you are black.