I'm not clear why the author thinks that "media sites, really" are the only SPA use case. Have they never used webmail (like GMail), map apps (like Google Maps), or social networks (like Twitter)?
But Gmail? Why do we need SPA for that? Receiving emails notifications could be websockets and clicking on email should go to a new page displaying the email. I dont know if the initial gmail was SPA or not, but the current version is very very slow and consumes a lot of memory to display some emails that worked even in terminal clients, remember Pine?
The same for twitter? I anyhow have to press "Load 39 new tweets" to load the new ones so why is it a SPA? Just for that notification? If you would give me a twitter client where I need to refresh the page to load new tweets but works faster and consumes less memory I will happy use that.
Because of a few simple interactions that are better without a page reload, people write the ENTIRE application on the frontend, with everything duplicated (modeling, validation, routing, error handling, etc).