If that were true, then the tongues of all his boots would slip over.
Some boots are just made with the tongue crooked and it slips over. I've got a pair of suede Indy boots where the left tongue slips to the right.
Crockett & Jones boots typically have the left side of the right shoe's tongue stitched down to prevent the slippage. (And of course the right side of the left boot's tongue).
I think the shoe contributes to it, but I think depending on how you walk, you can avoid it entirely. I have one boot from Alden that's more prone to it--all of my boots from them readily do it on the right, one does it very slightly on the left, but the tongue is thinner. And as you mentioned, C&J boots stich the tongue, so I haven't noticed it on them. Strangely enough, I just took off my boots the other day and the stiching on one of them ripped.