"Confirmed" snacks are food items that various DISers were able to get using a Snack Credit on the DDP.
Yes, all documentation lists a limited selection of items but states that they are examples, i.e. not the entire range of options; however, immediately following that list (online, at least) is the purple and white "Snack" symbol, with text to the effect that any item marked with that symbol qualifies as a "snack".
Can you imagine Disney reprinting the entire DDP brochure (never mind updating the website, don't get me started) every time a new food item was added to their inventory?