More pax going through the International means PA have more leverage to negotiate better retail contracts within the Terminal ie make more money per pax. Pax in T1 will be spending their money in the QF universe, PA will see none of it. Not being privy to whatever commercial deal PA have with QF, but you would think that it would be difficult to levy much of a passenger charge for pax that don't use your facilities ie PA lose money. Yes aircraft charges etc will still apply, but PA get that whatever terminal the aircraft goes to. It will be more difficult to finance T1 if you keep lettting new services operate elsewhere. PA would want an iron-clad guarantee that QF would move across before they spend a cent. Even then I'd be pretty wary, especially if QF had a few years to settle in to their T3 routine. QF do not do change very well. PA can see themselves getting painted into a corner not of their own making. They can thank the WA government for that. Perhaps Joyce will ground the airline if he does not get what he wants? He's got form.
(T1) QF Lounge facilities also very basic
Who's fault is that? They obviously didn't care too much about their existing international pax then.
QF want the "seamless" concept to work, because they are trying desperately to hide the fact that it is 5 hrs and 2 time zones from civilization before most of their customer base can use the "Western Hub".