yet another shoe question

[Dutchman]

i took some pictures of the various wreck recovered shoes to a leather worker here. she came up with an observation i had not heard of. Crediting GoF with all of the legwork has anyone seen this in the vertical but stitch at the heel. the top and bottom three or four stitches seem to be overlapped in the opposite direction. ie, the top three or four stitches overlap towards the outstep, there is the but stitch, then the bottom overlaps towards the instep for three or four stitches. something like this was/ is used to spread and reinforce a seam.

this is based on the following pictures from GoF's site. On the bottom whydah drawing of the back of the shoe, there is something odd going on with the stitch line. If you look at the closeup of the heel that is used to reference the but stitches, the top does not really support this, but whats going on at the bottom.

anyone????