Feedback IsAnyKindOfPrefab and the lack of prefab-ness in the prefab stage

It seems useful to me to have a function that tells you if an asset is in any way part of a prefab?

PrefabStage.IsPartOfPrefabContents works -- but only in the stage.

PrefabUtility.IsPartOfAnyPrefab works -- but not in the stage.

Probably the answer is for me to make a helper function:

Code (CSharp):

1. public static bool IsAnyKindOfPrefab(GameObject go)
2. {
3.     var stage = UnityEditor.Experimental.SceneManagement.PrefabStageUtility.GetCurrentPrefabStage();
4.     return UnityEditor.PrefabUtility.IsPartOfAnyPrefab(go)
5.         || (stage != null && stage.PartOfPrefabContents(go));
6. }
7.  

(Does that actually cover it?)

My real problem is that I find it unintuitive that none of the PrefabUtility functions return true in the prefab stage. I think I understand why: the prefab stage is a place where your asset isn't a prefab, but nested prefabs *are* prefabs. I'm not sure what benefit I get from this distinction. It seems like things would work more how I expect if the prefab stage worked like an empty scene with an instance of my prefab in it. I guess that's just how I'm used to editing prefabs (from before the new workflow), so that's still how I think about it.

Edit:
Another example that confuses me: how can I get the asset path for a prefab? might be PrefabUtility.GetPrefabAssetPathOfNearestInstanceRoot() or PrefabStageUtility.GetCurrentPrefabStage().prefabAssetPath(). If I'm adding some editor buttons, I need to check two things every time.