I think you are mistaken cowsaysoik. You can have your single page app load any content requested by the URL. Single page doesn't mean landing page, it is used to refer to sites that work like apps. The page is only loaded once,a nd then portions of the page are changed based on the users request.

I'm not confused I use newsblur like an app but it is behind a landing page when not logged in (https://newsblur.com/). There are plenty of other examples, otherwise it would be quite hard to get new users to your service as they can't find what your app is about.