Yes I do suspect the reason is commercial Titan, I've already said I believe it is due to staffing levels and tight turnaround times. JQ do not pretend to be anything other than a LCC and to expect them to provide the same level of service as a full-service carrier (even if Virgin et al offer a 'gate check' for chairs) is beside the point... it's not what they choose to do and they documented it accordingly.
As far as I'm aware there's no legislation to say what level of support is meant to be there, aside from that it should. Jetstar choose to provide less support than say Cathay or Qantas (examples you cited earlier) Until there's a law that says pax must be allowed to transfer at the gate then certain airlines are going to err on the side of less manpower/time cost... Again I'm not saying it's 'morally' right but that's how it is.
QF have a well-known policy for supporting wheelchair pax, right down to the pamphlets they hand out at check-in asking questions such as 'How do you transfer' and 'When do you want to change chairs' or similar. Doesn't mean other airlines have to offer it, QF are just choosing to be more advanced in their approach.
I think the sad thing about this case is no-one's gonna remember him doing Kokoda in 10 years, he'll be remembered as the guy who 'threw a tantrum' (to quote commenters online) and his other achievements will be overshadowed by this. By all means he should try to change policy where it is lacking, but I have a feeling he's also aliented a lot of the disabled community by acting the way he has, who would otherwise have been behind his quest for reforms.