Making a deposit/payment towards the purchase of a product with an "expected" delivery date is an acceptance of a seller's "all sales are final" terms. Failing to meet an "expected" delivery date would not be grounds for nullifying a contract unless there was a reason to believe that the product would never be delivered.

How is this hard for people to understand?

That being said, I would expect a respectable retailer to offer a refund in a case like this where the "expected" date was markedly wrong.

Nonetheless, GLWS

You are entering the period where you could file a complaint. In 6 mos, you may get to go before an arbitrator to have your complaint heard. If you haven't received the product by then, you may be entitled to a refund. So, I guess that could work out.

Either way, as I said, a respectable seller would issue a refund in this case.

Problem is, there was no "promised" date, only an "expected" date

And I imagine the contract the buyer agreed to had terms that stated their deposit would be forfeited if they decide to cancel their pre-order

The law regarding pre-orders is different from the law regarding sales. Bottom line, it will cost you more money and energy than it's worth to cite some FTC regulatory guideline, rather than a law (which varies by jurisdiction), before some arbitrator, who may or may not agree with you. The FTC is a regulatory agency, you act like you can call them up and they'll send out some guy who will fix your problems for you.