It's really not "clear cut." By the definition which you agree with, an HTML file containing JavaScript is served to the client without modification, and is viewable in any modern browser with a functioning JavaScript engine. The "web application" in reference is a server-sided application which controls and renders the content, as can be assumed based on context from the rest of that page. Namely:

> Any personalization or interactivity has to run client-side, which is restricting.