Do you know anything about how unaffiliated students are judged compared to students in NROTC?
The process is designed to get as close to an "apples to apples" comparison as possible. Objective criteria - Cumulative GPA, Calc & Physics scores (if you've taken them), and fitness test scores - are easy to compare.
The big difference is opportunity to create a subjective impression. Affiliated students have all year, which means the staff sees all the positives, but also the negatives. As an unaffiliated student, your interview and personal statement are your only two opportunities to make an impression. If you are prepared, you can make a great one; if you are unprepared, it is impossible for the staff to "fill in the blanks", since they don't know you.
Also, affiliated students are evaluated on both NROTC involvement, and campus involvement. Unaffiliated students can only be evaluated on campus involvement. This is fairly easy to normalize - it all adds to a total time & level of extracurricular activity - but again, the unit / scholarship board only knows the information you provide.