I don't really know where the Sq load theory originated, as far as I am aware of neither Greener or Burrard mentioned it, even though it seems to most often be credited to the "British". Sonds like some BS that Thomas may have come up with.
I think the most ludicrous I ever saw on it was in the premier issue of a Shotgun rag Peterson Publishing introduced some years back. Don't recall the author now or most of the details, but was a treatise on the 28ga as a Duck gun. Great emphysis was placed on the superior patterns produced by the 28 due to its Sq Load. He subscribed to the round ball equivelent as a Sq Load. Then, Rightly, told this could be found by dividing 16 by the gauge which for the 28 resulted in .57. He then stated this "Conclusively" proved the 3/4oz load in the 28 was the "Perfect" Sq Load. Now I don't really know if he was actually that Ignorant or just though all his readers were, but I learned along time ago in elementary school math as we studied decimal fractions that .57 & .75 even though they contain the same two digits, the reverse order makes them not even close kin much less identical twins.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra