No, presumably the client clicks on something, which calls an action on his server via xhr, which does some server-side logic (say, update the cart and compute a new total) and returns a json packet, which the client then uses to update the page.

Without knowing the specific details, I'd imagine the json response has directives for what static html to load if needed, which results in more xhr requests to get those files. The client side js simply needs to know how to process the json it's given, it doesn't need to know any business/persistence info.

What I'm curious about is how he handles urls (if everything is xhr, then the url will always stay the same, which is kind of a pain for linking to specific stuff, unless you do anchor workarounds like Facebook does). Also, I'd be curious if he uses the static html files as templates (injecting data into them clientside) or just has a TON of tiny html fragments.