BTW, before Burdick wrote the ACC, in early 1936, he defined T206's as -
"Set ss - Baseball players (white framed cards), Sweet Caporal, Cycle, Sovereign, Polar Bear, Old Mill, and several candy and gum sets of similar designs."
I think his main emphasis was to categorize cards in a way to make them easier to collect. Nothing more and nothing less. Today we might over-analyze things but that wasn't Burdick's idea. That is our idea because we are so freaking addicted
.