The amount of air that escapes through the hole is small in comparison to the amount of air that the turbo can produce dont forget if you are running half a bar of boost at 6000 rpm that engine is consuming a lot of air , it is there to give pressure to the boost control side of actuator , not a volume of air .

Once had an RS Turbo that the pipe had fallen off , it was boosting massively about 1.5 bar and it was not really noticeable that the pipe had fallen off in any other way .