When the switch fails it tricks the bike into thinking the clutch lever is always pulled in. This will cause your fuel gauge to stop working and, possibly, a whole list of other things that confuse the ECU. I think the jumper reproduces that type of switch failure- but it's been a while and you may be suggesting something entirely different. I posted about it with pictures of my repair to the switch years ago when I had the Roadster. I went looking for the reason my fuel gauge (and many other members here) stopped working and found the answer was- believe it or not, faulty clutch switch.
Here's what led me to that conclusion (below) and, on both the '11 Roadster and 2020 3R when I fixed the switch the fuel gauge began working again, immediately.
Here's some late night reading material that came up after some Googling results- after all, this is probably a Triumph thing, not just the Rocket3... https://www.thetriumphforum.com/threads/tiger-1050-fuel-gauge-clutch-switch.17629/...