Depending on the size of his operation, your seller may just be claiming "blind drop shipping" to make his operation seem more professional (not very wise on a private account.)

There might be some wee guy in a flat in Basildon, ordering items from Amazon or similar, one by one, as they are bought on eBay, and then shipping them out using the SD label. If they're being allowed to operate on a five day delivery schedule, that would give them time to obtain the products.