The only difference that I came across was in relation to "Computer white" and "Computer green" where one was the full intercept version for the UK Lightings as opposed to the Saudi Version. (So we were told)
As for the wire wrap why the first turn to include the insulation? doing that would have failed the fitter course but my memory fails me as to ever seeing that at Wattisham.
BTW the old DEC PDP11 computers used that method of wrapping as well?