The weighting of GPAs is a very imperfect science and class rank depends on....... the rest of the class. This is why SAT/ACT scores are so important. If you were an admissions board member, who would you think has a better chance of handling the academic work load at USAFA: Joe with a 3.9 GPA and 26 ACT super score or Jane with a 3.3 GPA and 33 ACT super score? All other things being equal, I'd bet my house that Jane is picked before Joe.
And you "Might" be wrong. Some people simply SUCK at taking standardized type tests. And the academy recognizes this. Also, the main factor you did not included in your hypothetical is; If Joe was in the IB Program or ALL of his classes were AP; but Jane's classes were normal traditional classes. The Joe's GPA would stand out as better.
But you did say "All other things being equal". So lets assume they have the exact same classes. There are 2 DIFFERENT POOLS that appointments are given from. The "LOCAL" state/district MOC pools and the National Pool. If Joe is in a state or district where he happens to be the BEST candidate on the MOC's nomination list, and Jane is the 2nd or 3rd best on her nomination list; the academy could pick Joe for an appointment and NOT pick jane but the #1 or #2 on her list.
But taking this even further, using the "All other things being equal" concept, what if they go to the same school, same classes, same leadership, same extra curricular activities, SAME EVERYTHING...... This is a straw argument because "ALL OTHER THINGS BEING EQUAL" Can NOT EXIST. There is no way that two individuals can be totally equal. Your comment about betting your house that the academy would pick Jane, has to ASSUME, that they are the very LAST 2 in the country to pick from.
My BET, which I believe has MUCH HIGHER ODDS OF WINNING, is that the academy would NOT PICK EITHER of these 2 individuals. The only way I see either of them getting an appointment, is if they were the "Principal Nominee" on the MOC list. In which case, the academy HAS NO CHOICE. They MUST GIVE an appointment to the Principal Nominee if that nominee is 100% qualified. (Academics, Physical, and Medical).
I have seen 4.0gpa and 34+ ACT applicants NOT GET an appointment. I've seen 3.5gpa and 27ACT applicants who DO GET an appointment.
Don't go down this slippery slope. All you have to worry about is:
1. Get the BEST GPA you can get.
2. Do #1 taking the most DIFFICULT and CHALLENGING CLASSES that are available to you.
3. Study and do your BEST on the ACT/SAT.
4. Be involved in extra curricular activities where you can perform in leadership roles.
5. Be involved in TEAM ACTIVITIES; especially sports. Also attain leadership positions in these TEAM activities.
6. Sell YOUR DIVERSITY to your ALO, MOC, and to the admissions board through your application. (Diversity; meaning how you differ from your competition and WHY YOU are the best choice for an appointment). Your ability to overcome adversity, your diverse experiences, etc.
Do these things, and your GPA, Class Rank, ACT/SAT, leadership, and the rest of your application and chances for an appointment will take care of themselves. Whether you receive an appointment or not, as long as you can HONESTLY SAY that you "DID YOUR BEST"; then you'll be able to live with that. Don't look for what the "Minimums" are. Minimum gpa, ACT, volunteering hours, years of sports, etc. If you LOOK for the minimums, I promise you that you WILL ATTAIN that. You should STRIVE for PERFECTION. If you aren't striving for a 4.0 unweighted gpa; or a 36 ACT; or to be the Captain and All State athlete, and president of your class or activities that you're involved in; and perfection in all other things........ then you're cheating yourself and you'll never be the BEST that you can be. Doesn't mean you'll reach PERFECTION. Simply that it SHOULD BE YOUR GOAL.
Best of luck. Mike