And it is not uncommon to be "frocked" In this situation a lower ranking officer is promoted to the next rank to assume the reponsiblity needed to fill a certain "billet" but they do not receive the higher pay until a later date. It's like, "Hey, we need a new RX director, but they have to be a major and you're only a captain...so we're gonna make you a major for now, but we're gonna pay you as a captain...dismissed!"
I've never served in the health professions as an officer, but based on my observations the promotions are generally very slow. In the miltary you have certain pay-grades that are really hurdles. It seems most military RPh are O-3 with some who a percentage who make it to O-4, but that is the hurdle. Not many RPh that make it past O-4. Just go look at the really high brass in military Pharmacy...no one above O-6 and not many O-5...most military RPh would likely retire as O-3/4 after 20 years
...just like civvilian pharmacy...not alot of potential for advancement.