It could be an app.

Minesweeper is an app right? Unit conversion? Color palette designer? Metronome?

The person you responded too didn't mention app though. They just said static. OP was talking about an app but the responded was hypothesizing about something static.

Anyway I'm not so sure "static" is a viable boundary between app and not app. A static page that does any sort of API request doesn't suddenly become an app imo.

Not really, is a offline chess page not an app? It seems like it would be closer to an app.