I don't think this statement is true,"you are fishing longer". I have fished with many spey casters and to tell the truth I think that my fly is in the water about the same length. It might not be out as far but it is in the water about the same
Most quarter their casts down stream and I go across. To me it seems the same. I get out a good 60 to 70 feet on my single hander and when I did the spey thing it was just a little farther.
But this is just the opinion of an old man and should not be taken seriously..