There is a theory floating around that the military used 9/32 drive to prevent theft (odd size, no use in civilian marketplace), but 9/32 drive preceded 1/4 drive in the evolution of socket sizes.
I have also often read of this theory, but never really believed to it.
I just believe, as you mentioned, that 9/32" drive preceded the 1/4" drive.
Snap-on for instance just stopped marketing the 9/32" drive in 1945, barring postwar industrial
lock button tools.
I do own a couple of Snap-on war time sets,but personally I would not use one for a GMTK even if I do have evidence of Snap-on 9/32" drive sockets having been supplied to the military.