Yes you're kind of stating the obvious there but what you're also doing is contradicting yourself. You've gone from "Time is the ONLY criteria" to a case of the pilot knowing fuel consumption figures and how much fuel he has onboard and estimating how much time he has left in the air. Without the knowledge of fuel consumption the pilot can not know how long he has left in the air.Why train pilots on fuel rate flow? If you LOOK at pilot training manuals, this is standard information for type of plane. Gallons or liters as the measurement unit, the pilot, as part of his fuel management, has to know flow rates in liters or gallons per minutes: at cruise, at full, at over-boost (variously called war-emergency or military power) and know the crucial flow differences at the various altitude bands, if he was a WALLIE or the different auto flow settings if he was a German. This is an essential (as in a matter of life and death) part of pilot training. The fuel gauges whether by weight gauge (spring) or volume (dipstick) gave an approximate measurement of amount of fuel available. Most car drivers never think of it, because their fuel gauge is fractionated in quarters and if they run out of gas they walk, but a pilot has to KNOW within 10% about how much fuel he has onboard for time of use. (There are also plane trim issues as tanks empty, but here we are discussing time aloft and how it is measured.)
Read again what I said...
"Basically your calculations are based on miles per minute, mine on miles per gallon. That’s not to say either method is wrong, just that we have different views on what is important."