I visited my JD dealer today and saw first hand what is available from the dealer. The blades that come standard on the 100 series lawn tractors are called mulching, discharge , bagging. They would be taxed to their limit to bag goose down. The other available set of blades from the dealer are called bagging and yes look as if they are for bagging.
Here is the kicker. I didn't weigh the blades but had each in my hand and I can say without a doubt the bagging blade weighs half again more than the standard 3 in 1 blade.
I cannot recommend the heavier bagging blade for a 100 series lawn tractor. There are just some things that don't feel right sometimes and this is one of those times.
In my opinion JD is making a mistake offering those heavy blades for their lawn tractor. They belong on a heavier machine.