The weight it is supposed to be used in conjunction with a snow blower cab/shelter, as the cab/shelter would cause the snow blower to be unbalanced. So I would imagine the two cancel each other out as far as added friction on the skid plates. But I am curious how a company can sell a kit that voids a warranty. It would also need to be in writing on the weight kit that states it must not be used on it's own. If no such documentation exists, then they can just go pound sand.
Balancing forces does not change the fact the weight of the snowblower increases with the cab and front weights. The drive system is therefore asked to do more to produce the same amount of work as before. Normal stress is Force/Area and you would be increasing the force over the same area. You would also be increasing Shear Stress where appropriate, which is also Force/Area. Remember these are cross sectional areas of the part.
All you are achieving by balancing forces is keeping the centroid of the snowblower as close to the original location as possible. You apply enough downward force to the handlebars and you are going to create enough of a moment about the wheels that the snowblower will begin to rotate and tip up. With the weight kit, yes you essentially cancel out the weight of the cab.
Ariens specifically states the weight kit is to mitigate the lifting of the front end in heavy snow. It does not make any mention that is was meant to be paired with the cab or that it's intent is specifically that. However if the cab is in fact between 10-20 lb then yes the weight kit(s) would be a good idea so that the machine is not prone to tipping the front end up on you.
I can see the dealerships argument, but I do not know enough about the drive system to really have a say in it unfortunately. I really need to take a look at a diagram and see what is going on.
It is very possible that the drive system can handle the 20lb of weight from the two plates. At the end of the day the elastic modulus of every part in that drive system is the decider of that.
I only brought this up because the dealers attitude on the phone was portrayed as if he had seen dozens of Ariens non-pro models in the shop due to this very issue with people adding weights. It seemed like a very abstract and methodical conversation to be a sales tactic to get me into a new rig....but who knows right?
There is much more to all this than marrying the word of some parts counter guy who throws out some claim. As stated in another post by someone there is no disclaimer or exclusion that secludes any certain model(s) of snowblower(s). So they would have to cover warranty work.