Yeah, My partner has just come back from a weekend in Melbourne and netted 60SP. It seems strange that when you go from 2x Seat or 2x Seat+bag fares, to one of each, the SP earn jumps significantly. Have just tried this on a ZQN-AKL booking and the expected SPs are roughly doubled so is not only on TT flights.
May do this on the next Auckland trip just for a laugh and see if it is accurate.