IMO it's not original.
As told above, the reverse lights (and the dashboard indicator light) wiring goes thru the bulkhead connector.
View attachment 1716318251
But, what's your problem? The reverse lights don't work?
In my case, I had a 3-speed trans and I replaced it with a 4-speed. So, I wanted to install the reverse indicator light under the dashboard.
I connected a wire onto the Z terminal on the inner side of the bulkhead connector and it works.