Sounds like they are short on storage space and want to make more money on what they have.

So they want you to apply 2 gallon of there new product, instead of your current 4. Will get you 4 lbs of S instead of 11.5, maybe they think you don't need sulfur and won't notice the difference. 

What are your corn yields? 11.5 lb S / 0.08 lb s/bu = 144 bu. Do you apply sulfur during the non corn years? 50 bu soybeans remove 9 lbs of S. Increase rate of thio to use full semi load.  Your 4 11 mix might store thru winter.

Could also switch to elemental S, for the bulk of your S needs, and apply 1 gal of there product for early season needs.