better persons could explain this better. there are 2 forms of resistance: the form resistance and the induced resistance
induced resistance is the one created by lift => higher lift (weight) will drive higher induced resistance
induced resistance is also inverse proportional to aspect ratio => higher aspect ratio will drive lower induced resistance
thus if the idea is to go up-wind like crazy it make sense to reduce weight and maximize aspect ratio, as possible.
But then i don´t think either the Epic Infinity or the Blade Fat Lady were designed with the idea of maximizing up-wind, i.e., they are not race kites. In consequence Epic/Blade didn´t went with the high aspect ratio solution as i guess this could limit other flying characteristics being persuit. As a low wind kite they kept an eye in the weight and thus the 3 struts solution.
having this said if Momi drops a line saying this is all wrong please believe Momi