I think the author is just sick of the bloat and pointless garbage that so many sites now include. I was all ready to argue with them from the title because, to me, an SPA is a Single Page APPLICATION, which can run without communicating with the server. There's places where those are useful, but the pointless, annoying trend of loading bits of pages via javascript that the author is calling out needs to stop.

If you're making an ecom system, don't, for example, make the product page load a page frame work, then load the description, price, stock levels and whatever else with javascript initiated requests. Instead render the whole thing server side and return it in one request. It'll massively reduce the load on your servers, perform better for your users, and make your pages more indexable. Feel free to use the fancy CSS animations the author suggests, at least they degrade sensibly, with no loss of functionality.