Your hypotheses are built around a clear separation between navigation and “self-contained processes,” but I don’t believe that that distinction exists.

Which is not to say you’re wrong — that’s not what I mean . I mean to say that deciding how to apply your principles is no more cut and dry than deciding what constitutes a “self-contained process.” Obviously picking a single entity from a selection is a single step that could be modally presented — it’s self-contained. Your example of viewing a photo is very in-between. Even reading a Medium story is in-between. Technically, it is actually a self-contained experience.

I don’t mean to sound negative and I very much appreciate the consideration you’ve inspired for me. I’m also trying to sort out that in-between core/nav screens and one-off/self-contained screens. So thank you.