The legal term is “consideration”. To form a contract you must have three elements: Offer, consideration, and acceptance.
Unfortunately, I’m not sure it would help here. They would argue their consideration is whatever online services are tied to the product, but even without that, the contract isn’t being formed at this point (unless someone is going through first setup, at which point they can still return it). The contract was already formed and this is an amendment to those terms that the original wording likely has weasel words to permit.
That’s not to say the consumer has no recourse, consumer rights are probably the best bet. If the previous terms don’t expressly grant them the right to take away access to all features in circumstances like this, it may be possible to find them in breach, but unfortunately EULAs are usually pretty toothless when it comes to penalising the vendor.