I worked for amex as an analyst for a couple of years. They do not (nor do visa or mc) have the ability to see itemised transactions from stores. They can see the merchant id (ie. the store), the amount of $, and they have a lookup table that will assign the merchant to a particular industry. That's pretty much it.
This is blatantly false. My Amex online account lists itemized receipts for at least some retailers (I remember offhand all of the office-supply chains).