"I would have hoped that any machine advertised as washing a 4.1 cu.ft. should be able to wash the same amount as a machine of the same capacity.... "
What this means is that the machine is not actually 4.1 cu ft (thus the I.E.C. designation), and since it does not have an agitator, it will wash as much as a comparable 4.1 cu. ft (D.O.E measure) rated washer. My guess is the machine has the same 3.5 cu. ft tub as the regular hydrowave washer, they have just removed the agitator in favor of the "infusor", which takes up less space, thus leaving room for more clothes. THat's how manufacturers get to the I.E.C. equivalent of the D.O.E. rating. Basically, makes it look bigger than it actually is. So a 3.5 cu. ft D.O.E. rating is equivalent, in this case, to a 4.1 cu. ft. I.E.C. rated capacity. In any case, it will hold more clothes than the 3.5 cu. ft D.O.E. agitator model, but it's not really any bigger than that same model.
Take the new Kenmore 800 washers. They rate them at 4.0 cu. ft. I.E.C., yet it's the same damned washbasket other 3.5 cu. ft. D.O.E. rated Kenmore washers in Sears' lineup use. What's the difference in this case? The rating scale....I.E.C. vs. D.O.E. The machines are basically identical capacities. The way it's presented is quite decieving, as it's not really a bigger machine.