I recall reading (somewhere) that with some 12 ga. 2' doubles it was believed(speculated?) that barrels were proofed in the white and when finished by the gunmaker, the barrels' exteriors may have been further struck to reduce weight which would have left bore measurements intact. I'd verify the MWT as it does sound like a misprint. Two pieces of copy paper stacked together measure .007". Here's an article that discusses the 2" 12 ga. guns and it mentions wall thicknesses with one gun measuring .012".
https://shootingsportsman.com/short-shell-12-2-guns/Gil
