He is talking about having a large open source application that you can browse the code to see how things get structured. A simple TODO app and a real-world app are very different, and most TODO apps would turn into spaghetti code.

Plus it is nice to see the little tricks that are done to make the code more readable or improve the overall design.

Both are my metric? Is that not obvious? I'd like to see a large scale production ready application that I can learn from. The open source apps from builtwithangular are pretty useless since they are all just slightly more complex than a todo list.

A large, open source app. For evaluating how to solve big-app problems, size, on its own, is meaningless, except to show that the hard problems can be done, because it doesn't show how; and open-source, on its own, is meaningless, because it doesn't run into those problems. So adamnemecek needs both to fit his query.