Here's how I know that: I recently bought a woven wiring harness for my little '63 Midget - got it from Moss. As I was installing it, I came upon a question. Luckily, I never throw anything away until a job is finished so I had the plastic bag in which the harness came. It had the factory parts number on it as well as the Moss number.
While the Moss tech guy was researching my question I called both VB & British Wiring to check on their harnesses & gave them my factory part number to check against what was in stock in their warehouses. Both had the exact same factory parts number on their plastic bags (VB's even had the Moss number on theirs as they buy from Moss).
I have the phone number of the factory in England as several years ago British Wiring (before they were sold) had a custom harness built for me & I had to talk to the factory while it was being built. So, I called the factory & gave them the factory parts number on my plastic bag - it was their parts number, the one they use in-house while they're building harnesses before they ship them to Moss, VB, British Wiring, etc.