I went & checked the old vt wiring. That wire in your hand in post 23 is the body earth.
You can see that there are 2 different looms. One is for the the positive. The other negative (the one in your hand).
Also the the one in your hand would be part of the loom that goes to the negative post on the battery.
I had my vt apart a few years ago ( l was changing the looms for climate control). End of the day, l was tired & l put that earth strap on the positive blew the fuse box relay. (What the fu#k?) Realised my mistake, Corrected the wiring then replaced the relay & all was good.
Anyway, hope this helps. The photos l took where crap, so no point in uploading them.
Good luck.