As with many things in "modern" web development, "endless-scroll" is not really endless (as nothing is endless). It's a technique similar to how Facebook, Twitter and others continue to automatically load content when you reach the bottom, giving the impression of "endless" content. Of course, even Facebook and Twitter would eventually run out of content to show, but somehow that pattern got the name "endless scroll".
See also: isomorphic, real-time, serverless and countless others examples of poorly named concepts in web development.