It’s not true or false per se: you can structure the maths in any way you’d like, sometimes they could work to describe the scenario that the boot tax describes, sometimes not, it’s insane that we’re even talking about a curve & people arguing that only this section of the curve is real
I have no doubt it was intended that way! But in practice, in The Discourse, it has come to represent a very specific claim about consumer goods. That’s why it has its own wiki page and everything. Poverty taxes are real, but the SPECIFIC claim, described below, is generally false.