Sprite Atlas, UI & Batching

We are moving our sprites to the 2017 Sprite Atlas system and ran into some weird behavior when it comes to Sprite Renderer and UI Image objects (that expect a 2D sprite).

Sprite Renderer

If we first examine the difference between 2 sets of sprites using the Sprite Renderer. One set is in a Sprite Atlas and the other is not.

Here we have 10 sprites which are all not in an Atlas and so it counts 11 Batches and 0 saved by batching.

Here we have 10 sprites which are all in an Atlas and our count has changed to 2 Batches and 9 saved by batching.

This all looks good and is what you would expect. Unity is doing some magic behind the scenes to use the sprites from the Atlas.

UI System Image

Now lets looks at what happens when we use exactly the same sprites but use the UI system.
So here we are using the UI system Image and the same set of sprites that are not in any Sprite Atlas. As you would expect we see that same numbers: 11 Batches and 0 saved by batching.

Finally here is what has us scratching our heads. These sprites are all in a Sprite Atlas and are displayed in a UI Image. The Statistics window states here that there are 2 Batches yet 0 saved by batching!

Now I created this project specifically to test Sprite Atlases as we were running into some weird behavior with UI Image Sprites and batching in our main project. I haven't been able to find anything about this online so I am wondering if there are any known (unknown?) problems with the new Atlas system and UI Images.