While such a policy might maximize economic utility I think you’re correct that it’s advocates gloss the obvious physical - but also social - constraints.
Sometimes gas (or whatever) just can’t be delivered for any price. Since demand obviously drops off with price, it’s hard to believe suppliers could justify mammoth investments in delivery infrastructure.
More importantly, such a policy means rationing a essential resource proportional to wealth. Those with the most get what the need; the well off get a little at a painful price; those struggling under normal circumstances just go without. The argument does that a little at a painful price is better than none at a artificial price. I think that misses the size of the lattermost group, and the risk that expressing a fundamental inequality between humans during exigent circumstances - that if you don’t have money, you can’t have gas or heat, or whatever it is - puts social cohesion in jeopardy. Rationing resources either by explicit (1 gal per customer) or implicit (first come first served) policy might be economically inefficient, but socially expedient