Why wait? It takes time and I don't like wasting time. I also drive in areas where gas stations are few and far between so I often need to ask "can I make it to the next station or do I need to buy $5/gallon gas in Bridgeport, Ca?"
To each his own -- it takes less "wasted time" to fill up less fuel than waiting to fill a complete tank.
Giulia does not have fuel float(s). She has electronic sensors.
I thought that might be true -- and is why my original statement noted: "This is because at full, the fuel level in the tank is "higher" than the actual highest limit of the fuel level float, or whatever sensing device is used to send data to the gauge"
I made some measurements of the fuel sensor output while I added 1/2 gallon at a time to the car and got very confusing results. I'll process the measurements later but one thing that was really obvious is that the output has a considerable amount of hysteresis as I had to add quite a bit of gas before the reading changed at all. I presume the hysteresis is there to mask apparent fuel level changes when the car is on a slope or accelerating.
I have found a similar "buffering" of my oil gauge in my BMW -- if I add 1/2 quart, when low, it will not be immediately reflected on the electronic level gauge.