They could have the lounge available for use prior to immigration. Makes it a bit tricky if you then stay in the lounge too long and can't get through immigration in time. Seems a little odd.
But no different to Darwin Airport's Qantas lounge (for International), or to some degree Singapore/Bangkok lounges (lounge is after passport control, but before security screening). I doubt International outbound immigration would take long at OOL - especially with it only handling a few flights per day. Plus the Jetstar Lounge ppls would quite effectively round people up early enough for them to go through immigration.