He does it on purpose for fun, it should never catch him out as I said because you'd have to stamp on them to do it
Yeah, so it's perfectly safe because it only happens when he does an emergency stop? No. Seriously not buying it, whether it's in front of a school, or when someone in a new Audi anchors up in front of you on the motorway. It's dangerous and any MOT tester who knows their stuff should fail it.
DH - Explain Please for us idiots...
Right, as standard on the 1.8 driver and above (IIRC) there is a brake compensator unit through which the brake lines to the rear run. Under normal circumstances the force to the rear axle is reduced, as you ALWAYS want the fronts to lock before the rears (even if it's funny when the rears lock). This is because the weight in the car is more over the front axle, than the rear.
When there are fat birds in the back of the Golf2 the weight balance changes, so the rears can be more effective than in the car's unladen state. When the ride height goes down from the normal 'unladen' state the valve opens up, allowing more force to be delivered by the rear calipers.
So, as a side note to this explanation, when you change the ride height of your Golf you should ensure the compensator valve is closed up, so when you put fat birds in the back of your car it opens.
As outlined by DOA earlier, if you run very low then you have virtually no travel and thus the valve should be closed most of the time, or under unladen/laden the brake bias will not be right.