I agree that it doesn't work, but you can't compare US airlines. US airlines don't board a 737 in 14-20 minutes. This is what Qantas does.
Starts at -20, finishes at -6.
If Qantas boards faster than US airlines, it would be due to various other factors, nothing to do with priority boarding but mostly to do with the immense amount of carry-on baggage that the US has to to deal with which slows everything down. Reasons for this:
* AU: Lack of baggage fees encourages checked luggage
* AU: Most domestic travelers are on a single segment without connections, and thus more willing to check luggage compared to the US where connecting flights are the norm and many US airports have a poor reputation for luggage handling
* Connection times in Australia are long enough and airports generally competent at handling connecting baggage, so those who do have connecting itineraries are comfortable checking luggage
Does Qantas board from the rear on the tarmac? I travel domestically so rarely that I've forgotten if they do this or not. This would be unheard of in the US for security "reasons" (and also generally poorer weather making it less viable).
Qantas also has a much lower load factor than US airlines, which are almost always at 100% these days due to extremely aggressive yield management.