"Stacks" pattern name is confusing
The HIG has a design pattern called "Stacks", but the design pattern doesn't correspond to GtkStack. This creates the potential for confusion.
We could potentially just rename "Stacks" to something else. A stack is just navigation that's one level deep, with a parent page and multiple child pages. Alternative names could be something like "Shelf" or "Parent/Child Nav".
Or maybe the pattern is "Browsing" and we should document the different types, where one type would be consequtive browsing through a prexisting tree/network (ie. file or web browser), and the other would be constrained browsing within a tree that's specific to the app (ie. what stacks are).
The latter is more or less what the Material Design and iOS guidelines do.