Am I correct in understanding that NGPL mostly goes for Propane (LPG), along with the top fraction from crude oil refining? If this is so, then am I also correct in concluding that it appears that the supply outlook for Propane, at least in the short term, is actually improving?

Another question: If my above assumption is correct that NGPL mostly goes for Propane, then given that Propane mostly functions as a substitute for NG, is it really meaningful to include it in with the other liquids discussed above? Is this not, perhaps, a case of apples and oranges?

I'm not sure about the relative fraction of butane vs. propane, but butane is slightly heavier, and it can be blended into winter gasoline. It can be counted towards liquid fuel supplies.