I only fly lighties, but wouldn't you get to a certain distance down the runway, get an odd feeling about lack of acceleration/airspeed and runway remaining, and I dunno, manually increase thrust?
Not neccesarily. If they were going off the short runway in YSSY then the aircraft could have had insuffcient thrust set while at the same time feeling positively lively compared to if they had gone off the long runway.
So....insuffcient thrust can provide quite brisk accelleration compared to the correct amount of thrust on a different runway. Hope that helps explain how it can happen Typhoon.