CraigD - "that more pounds could be shown to push on less square inches of a smaller bore to end up with the same velocity for the same weight of shot. "
More pounds are not pushing on fewer square inches. The same pounds are pushing on fewer sq. in. Thus, total force the same, but force per sq. in is less.
Some other questions come to mind. How far up the shot column does the "force" cause the pellets to become deformed? What happens if, instead of a column of individual shot pellets, you have a lead cylinder of the same weight? When, and if, does a shot column begin to behave like a solid lead cylinder?
There are fewer pellets in each cross sectional area of the smaller gauge, so fewer pellets on the "bottom". Does this decrease in number have an effect on total deformed pellets? If both the small gauge and the large gauge were fired from a cylinder bore, would you get a greater dispersion from the smaller bore because of deformed pellets becoming outliers from the main pattern. Think about what happens if you carry this to absurd extremes - that is, bore size is decreased until it equals pellet size or increased until you have just one layer of pellets.
I think there is much that is not known about the process. There is no shortage of opinions, anecdotal evidence and some non-controlled empirical evidence. I'm biased toward theoretical constructions validated by evidence from controlled repeatable experiments, which is what I think Wonko was saying.