Yep call BS on that one. Military in uniform on duty - No ASIC required.
It depends on whether the airfield security people know that or not ... a few years back I was part of a 7 aircraft push passing through Ayers Rock airport - I had an ASIC but most of the others just had military ID. Even though we'd just landed and parked together, all wearing uniform, flying military aircraft, it was a major drama for us to get to and from the tarmac area.
The bloke was just doing his job, but not fully aware of the rules regarding military - the silly part is he couldn't just make a judgement call and give us the go-ahead based on common sense ... he was hamstrung by a ridiculous system that really achieves bugger all. As you say, LB, if someone really wants to get up to no good, lack of a card isn't going to stop them.