I can't think why this would have happened, can the pilots please help me understand? 2 aircraft departing Wellington NZ today. One taxis north for a runway 16 departure and the other south for a runway 34 departure. Both left the gate at around the same time and the winds were a very light crosswind at 4kts/130º as seen in the pics. QF172 then sat idle at the northern end of the airfield for about 15 minutes and then taxied to the southern end of the airfield, via the runway initially and then back onto a taxiway as shown. All aircraft movements were departing and arriving on 34 during that time. Similar aircraft being an A320 and B738. Could load or weather or SOPs be a factor? Time was approx 1600 local. A Sydney bound QF flight had departed on 16 about 40 minutes earlier, if that helps.