True the receipt protects against 2) more than 1) because the car's tank does not have an accurate guage.

I remember listening to a story once about a fraud at the gas tank in which the normal amount of gas was only given out when requested in an even increment a five gallons which was how much The Regulators requested when they came and tested a gas stations pumps. they were caught after a spicious regulator requested an odd amount of gasoline and got the wrong amount.

with a combination of receipts and camera/ML classification that classifies when a customer is filling a tank versus filling their car will allow avoidance of weights and measures regulators. This is a problem I foresee.