That seems to be the Luigi style
I think we had this dicussion some years ago (maybe it was in the old Gileraclub forum)
Also the Saturno has a gauge with or without this extra resistor.
I had a funny overheating probem at those times and thought it was a problem with the gauge and /or the resistor.
But it was something completly different.
Looks like Luigi has once decided to add this resistor.
Maybe because he used a different gauge from that on.
Or because he thought the temperature which was shown, was to somehow to high.
We will never find out, i think