What is a single-page app?
The advantages that this approach gives are that the client can run something in the background between page transitions, and the client does not have to re-download and re-render the entire page in order to swap only the main content. Unfortunately, it also brings drawbacks, because now the client is responsible for all state changes. For the synchronization of such changes across the entire interface, it must know when to load the data and what particular data. In other words, a server-generated app is conceptually a way simpler thing, thanks to the REST service + JS client.