I think the real issue, at least here in Canada, is that gas is sold "corrected" to 15C. So, in winter the pump shows, say 10 litres, but that is what it would be at 15C. The temperature of the gas in the storage tank might only be 2-3C so you get less fuel that you pay for. Of course, in summer, it is the opposite but the temperature of fuel in a UST would be not more than a couple of degrees warmer than 15C so, the error in your favour in summer is much smaller than the error in their favour in the rest of the year.
Ans I, too, have never seen my warning light on in either the cab or the coupe but I always rely on it in the Cayenne and Cayman.