There is more to it than that. The service academies have a core curriculum that all cadets/midshipmen take that is heavily oriented towards math and science (calculus, chemistry, etc.) as well as advanced English courses. A cadet may validate those courses already taken---that is "validate" as in take the final in the course and achieve a certain minimum grade---not transfer credits. In doing so, this frees up time to take advanced courses in the offered fields. It is possible by validating enough core courses to get a masters upon graduation but it is tough as most Associates are not that demanding.