You are correct.  I works like you think it works.

I had to use a "Urea" and "Urea2" products to get my two bin to work.  If it would auto switch bins like Raven that would be sweet! 

I can't be the first one to run one product in a twin bin box and find this "problem".  To me it is a problem, but must not be.  maybe I will see what they say about it today. 

Only way I have figured it is to cut the rate in half for each bin and then both bins would be on all the time and autoswath should work.  But getting half the product in each bin would be a trick in it self.

ie. if puting on 300 lbs acre, target rate 150 lbs for each bin for a total rate of 300 lbs.  Autoswath would work then.