Amazon are just weird like that. They're obviously not primarily a gaming website and staff are not usually equipped to answer that isn't anything to do with... well, books, I guess. When I've had problems in the past with PC components that I've bought from them, they've been like "Yeah, err... you what, mate? Garlic bread?"
They're ruddy brilliant when they have a clue what the hell I'm talking about though. I've been shopping exclusively with Amazon since they did me a favour and refunded me on a dodgy projector that I'd purchased that had suddenly died after nine months of use.
Anywhoo - no idea why they would remove the DLC listing information from the page. Then again, it baffles me as to why they change their product prices several times a day - even by just a few pence. They've confirmed that we'll receive our DLC though... so I'll just put this one down as Amazon just being dippy ol' Amazon.