There’s a tendency, particularly for networkers, to classify applications by the protocols they use. If it uses HTTP, it must be a web app. The thing is that HTTP has become what it was intended to be: a transport protocol. It is not an application protocol, in the sense that it defines application messages and states. It merely transports data in a very specific way.
That’s particularly important in the age of the API and, increasingly, the age of things that might be using APIs. You see, APIs are primarily data centric constructs while web pages (think any HTML-based app) are document centric constructs.