What kind of batching is used with Sprite Atlases?

I thought sprites within the same spritesheet used Unity's dynamic batching system (as sprites share the same texture file, when given the same material reference they're batched together), but then I saw a blog post saying dynamic and static batching has nothing to do with sprite batching.

I tried it in Unity, turning off both dynamic and static batching and creating a scene with two sprites from the same Sprite Atlas. The result: only one draw call (and the other is marked as being saved by batching).

Then, if Sprite Atlases don't use dynamic batching, what kind of batching do they use? (batching is clearly taking place although dynamic and static batching are disabled)