Not the same thing, really. This is a potentially complicated area, and particular laws or regulations, or factual twists, may kick in the change the default rule in particular circumstances. But as an initial principle of contract law, if the seller makes on offer on specific, clearly communicated terms, acceptance of that offer is deemed acceptance of the offer in its entirety (that is, of all of the stated terms).
I knew that sooner or later a lawyer would show up and make precisely your claim.
Yes, it's a potential complicated area turning on particular laws, regulations and factual twists, and your assertion that the seller's offer has to be accepted in its entirety is generally speaking sound.
But will you also agree that contract law, generally speaking, as it pertains to the simple sale of goods and services between a buyer and seller who come together for a one-time transaction, does not require each party to engage the services of a lawyer to parse the precise meaning of the offer and its acceptance by the buyer?
Common law, UCC, and public policy more generally want these kinds of sales to be concluded with as little friction as possible, with the lowest possible transaction costs.
Having a seller unilaterally opt out of his obligation to perform his contractual obligation (as that obligation is commonly understood), while keeping the buyer's money, does nothing to facilitate commerce.
Which is why, generally speaking, for these kinds of transactions, the policy is to hold each party responsible for performing.
The buyer is responsible for paying (and being able to prove he paid). The seller is responsible for delivering merchandise as promised, with all the implied warranties as to its advertised quality and performance and so on.