I am not sure any one will be able to give you a definitive answer as to what does/does not qualify you for a prep school or prep school scholarship... What I have heard is that they are offering prep school/scholarships to individuals they feel could use the extra support; whether academically, leadership or conditioning; to be successful at the SA. Therefore, you could be an ideal candidate as a student that hasn't been introduced to college level (AP/IB) courses in high school.
That said, I have also seen on this forum that some feel that the difference between prep school at an SA (USAFA Prep/NAPS...) is typically given to students that need additional oversight in the extra support to be successful; whereas those that get prep scholarships are typically students that demonstrate academic rigor or success rising to the challenge of prep school independently...
Again, I have not idea if either of these responses or thoughts are accurate... however, they seem like good logic...