I don't think there are any devices that are showing it for these app types at this time, but I recommend including them to "future-proof" your apps.
We expect to be using them in Data Fields on Edge in situations where you are previewing Data Field layouts while a different set of fields is loaded.
There are situations on the current products where they really should be using the App Icon for Widgets when viewing the widget loop during a native activity when the widget cannot be loaded.
I don't know of anywhere I would expect them to show up in for Watch Faces, but they could possibly be shown in the menu when selecting the active face.
