The length of the pin determines the timing between the on-off shutting off and the sear releasing/catching the bolt. By keeping the pin longer, you ensure that the sear is far enough up on the lip of the bolt when the on-off opens to recharge the chamber that the forward push on the bolt won't cause the edge to hit the tip of the sear. It will actually hit a larger area of the sear. Spreading the force over a larger area reduces the force per area and reduces the amount of wear and damage that can occur. A short on-off pin allows the sear to hit the lip of the bolt like a knife. Eventually it wears the knife edge and it becomes rounded or broken. When this happens, you can't control the operation of the trigger.
With a longer pin you need a bit more force to kick your finger forward far enough allow a full recharge, which is why a high pressure tank is so desirable for reactive trigger enthusiasts. It's definitely the safe way to go, though.
Except for the Automag in front, its usually the man behind the equipment that counts.