I suspect that that is straight-up illegal in two different directions: it is unlikely that the credit card company would be pleased to find out that these folks are trying to use a credit card signature for something else, and I'm pretty sure any lawyer could get such a contract thrown out with exactly zero effort, if it truly is framed as just being the receipt that you use to pay (a contract has to be intentionally signed by person who intended to agree to it in order to count for anything)
IANAL either, but you are not wrong. I know about this because I was involved in a lawsuit that involved contract law. In order for a contract to be valid it is not enough to have a document with a valid signature on it. There has to be an actual "meeting of the minds". Both parties have to actually intend to abide by the terms of the contract at the time it was signed, which logically implies that both parties have to know the contract's actual content.
The real underlying strategy here is to leverage people's general ignorance of contract law in order to intimidate them into thinking that they are contractually bound when in fact they are not, at least not legally. As a practical matter, the need to pay a lawyer often trumps the actual law (another lesson I learned the hard way).
Interesting theory. And indeed, it is just. But On its face it negates the validity of any drive by scroll down to accept contract, but I believe they are binding to some extent at least. Maybe the scroll down click is considered at tacit acceptance of what’s inside.
(IANAL, could be wrong)