I know this is a leather thread, but DW why is it that in a lot of bespoke shoes you see a split where the heel joins the sole? This transcription reminded me of this. I was under the impression that the sole extends all of the way through to the back of the shoe and the heel is attached over top of the sole. On bespoke is the whole heel its own piece? What are some of the reasons for this? Also, I noticed this is present on RTW G&G shoes, is this functional, or just a nod to its bespoke big brother?
As promised...from Golding Volume IV fig. 42...
Outsoles may be cut entire or with piece soles--3/4 sole and heel piece.
Fitting together those pieces was done several ways. The first and most obvious is bevel the heel seat edge of the outsole in one direction and the piece sole at an opposing angle. This was probably the most common.
The other way is/was known as "springing" and is illustrated below:
The seat end is cut square and the piece sole edge is cut concave. The outsole is secured at the seat end (as in fig 42A) and then the piece sole is secured in the center with some overlap as in fig 42C. The corners of the piece sole are then sprung back to create a tight physical junction between the outsole and the piece sole as in fig. 42D. This was known as a "stunt join."
I don't know if this answers your question or not, but FWIW...