First of all, I know you disagree with additional ground wire I added to the frame on my R3T. This in spite of the fact that the manual make two specific references to frame grounding....
We've been through this before - There is NOTHING on the bike's electrical system that connects electrically to the frame
What
YOU are doing is a 'short-cut' to improve your ENGINE grounding, it does absolutely zero for any other electrical component.
Engine ground is predominantly for the starter, spark plugs and the Oil Pressure and Neutral lights - everything else reports via the wiring system to the battery negative
What you are doing, as opposed to directly improving the ground to the engine directly, is to connect a short wire to the frame, then have the frame connection to the engine complete that circuit.
That means painted surfaces, dissimilar metals etc come into play. Do you notice this? Most likely not, just not good practice - especially when its just as easy to connect directly to the engine since having the frame itself being grounded is completely irrelevant
Without that new frame ground, standard system, there is ZERO current that flows through the frame, to get to the engine ground to return to the battery.
As for the comment in the manual - I believe you are referring to the GENERIC section (who knows how many eons ago that std claptrap was first penned) on page 1:14 that makes that reference to frame; I invite you to please enlighten/educate me (sincerely, not sarcastic) to any system element that connects electrically to the frame. That statement has no basis in regard to what is actually ON the Rocket (or frankly any other modern Triumph)
This is image of ground cable I found on another R3 site discussing the ground cable mod:
The big diameter is battery negative to engine; the smaller is to the negative distribution system
This on a standard - again, not sure if that is the same for the Touring
But for sure, however the main scheme connects at the battery end (whether directly crimped into lug, separate lug or like this) the engine ground end is irrelevant
Parts Fiche shows ground cable (item41) to at least appear to be same as per above - also same part number for R3 Classic/Roadster & Touring