I think this has less to do with whether the major prepares you for the exam than with the raw talent of the people who choose various majors. That's why physics/math comes in first. My theory, anyway. The best advice for those who want to go on to law school is to study something you're very interested in and good at. It will help you get a good GPA, which counts about as much as the LSAT in admissions. It will make college intrinsically rewarding. (Try to make whatever you do intrinsically rewarding.*) And it will give you an opportunity to find out more about your own preferences which you will need to have when you get out of law school and find a path within law. It will also give you the ability to be drawn away from the idea going to law school, which is certainly not a bad thing.
*To think more deeply about what it means to do what is intrinsically rewarding, read Mihaly Csikszentmihalyi's book, "Flow." At page 49 of the 1991 Harper Perennial edition, he describes the 8 components of flow:
First, the experience usually occurs when we confront tasks we have a chance of completing. Second, we must be able to concentrate on what we are doing. Third and fourth, the concentration is usually possible because the task undertaken has clear goals and immediate feedback. Fifth, one acts with a deep but effortless involvement that removes from awareness the worries and frustrations of everyday life. Sixth, enjoyable experiences allow people to exercise a sense of control over their actions. Seventh, concern for the self disappears, yet paradoxically the sense of self emerges stronger after the flow experience is over. Finally, the sense of the duration of time is altered; hours pass by in minutes, and minutes can stretch out to seem like hours. The combination of all these elements causes a sense of deep enjoyment that is so rewarding people feel that expending a great deal of energy is worthwhile simply to be able to feel it.