No, he was not a tax attorney. I agree, it seems outrageous but it doesn't seem completely impossible. If the servers are located in the US one could argue that the company is doing business in the US.
If you were providing services to AWS - that would "be doing business in US". I don't see how renting a service (AWS) from Amazon is "doing business in US" any more than would be buying a book from Amazon.com N'est-ce pas?