I didn't know that Ray, interesting observation.
Jerry, as with alot of things perhaps the answer is a little more obvious. A little like the OB Demo, the onions are prepared way ahead of service and sit for oxidising for a while. This will help to soften the onion up, prior to it being used. Also, when you chop your onions and leave them to sit, break the layers up to allow the air to get in between them.
The only other thing I can think of is the onion itself. I know the IG buy onion in 25kg Netted Sacks. They are your basic market onion and fairly young in growth.