The USPS Store's website is messed up (has been for awhile). I don't even bother with it much anymore. If you want a specific item, it's easier to phone in the order than trust the website. It's usually more accurate, too, as they can give you stock numbers for specific items that aren't even shown on the USPS Store's website.
I can't understand it, but the USPS
ebay store is even worse, not having several new products available for sale or pre-order. It seems to me that both these websites should be updated concurrently, but that's apparently not the case.