Exactly, I know exactly what you're trying to say Bob but in this case i'm thinking in terms of torque.
I was thinking about this last night. I think the reason this 'works' or rather people get away with it is:
1) the auger is big and heavy, it carries a ton of rotational mass which helps it resist shock loads, and the chain has some additional give, so even though the gearbox is seeing higher torque its not as much abuse as direct drive
2) The limiting factor is the engine torque which is sized to the gearbox (probably oversized to the biggest engine possible, 332?)
3) the belt slip ultimately limits torque to whatever the transmission capability of the belt is, I'd guess about 25 ft lbs? I have in a pinch made mine squeal/ slip the belt but thats really givin' er.
upon further consideration i'd guess its probably not going to hurt the gearbox, maybe put extra load on it, but more importantly does it actually work better? I've only got the 16 hp single so some folks with the big twins might have different experience but my '49 will bog down the engine way before it stops chucking snow, not sure i'd want to go that direction.