A question I had was how he made the correspondences between points in the two bolts. I have a hunch that he just traversed the two lightning bolts separately

A question I had was how he made the correspondences between points in the two bolts. I have a hunch that he just traversed the two lightning bolts separately and said point 1 in A corresponds to point 1 in B, ... Point N in A corresponds to point N in B, etc. if this is the case, you would expect dx and dy to grow as from top to bottom and hence his reconstructed depth to become closer from top to bottom, which is what happens.