There's no published policy that correspondence is a prerequisite, either. In my wing, they still preach the "correspondence is a must" but the reality is, they will send--and have sent--people who have not done the online version before they will ever give back the slot. Part of what I told my CC in our meeting was I have a really tough time justifying doing it when we have sent people straight to in-res who do not even do half the work I do on a daily basis and are considered "behind their peers" on all fronts. So the hard workers/high achievers have to do more work while the typical lazy asses get to skate by yet again. This may not be the case in other wings but it is definitely the case here.
I understand that going to the IG is a ballzy move and you'd better bring your A-game...it is not something to take lightly. But I have a hunch that just a whiff of someone going to the IG with this would get management scrambling, at least in my neck of the woods. Especially if people like me (with a clean paper trail, no skeletons in the closet, a good reputation, and a strong performance record) launch the complaint if ultimately denied the chance to go in-res, it gives the complaint some teeth. It may blow up in the end and have negative consequences, but I will accept that. Better to fight the good fight than live my life succumbing to every absurd demand the AF makes--especially demands will no real reg or written policy to back it up.
Panch--I'm not going down that road currently and don't need to (I'm a first-year Capt). I would absolutely try to resolve the situation at the lowest level before taking drastic measures. I'm just speaking hypothetically, as though someone was at the point of their "last look" to go before their majors board.