The language parent post used may be imprecise, but the effect is largely what oil extractors are now seeing.

Global oil prices have fallen due to demand descruction. Total quantity of oil consumed is down as well. Revenues, as P * Q, are down. It's a compound effect.

Saying that both supply and demand have fallen is incorrect in an economist's sense as to an economist these are functions. Shifting one function (usually expressed as a "curve") moves along the other curve, even without a change in that function.

Confusing, I know.