Chopper, we are clearly looking at it from the point of view of different protagonists. Let's be a bit clearer.
Red (attacking) puts in a grubber kick for the corner. It just catches a Blue defender's leg as it clears the defensive back line, and then dribbles into touch 2m out. Red winger picks up the ball on the 2m line, walks back to the 5m line and takes a QT to his inside centre on the burst. Centre scores - all is fine.
Same scenario, but where the ball does not hit a Blue defender. Blue fullback picks up the ball on the 2m line, dashes to the 5m mark where the TJ has his flag up, and takes a long QT infield to the opposite winger who's covering across. In that case, the QT has to be pulled back, because it has been taken in front of where the ball crossed the touchline - albeit that that is the mark for the line of touch.
If the blue fullback waits at the 5m line until 2+2 exists, then hands the ball to his hooker who immediately throws in straight without any call being made, then play continues, the lineout having been duly taken, albeit before the player in the tramlines had a chance to get into position. The opportunity to take the opposition by surprise is its own advantage, so we see how it all unfolds from there.