Batching for two or more sprite atlas is calculating incorrectly

Steps to Repro:
1. Play the scene in the attached project > game window > stats
2. Observe that the batches are '4' and saved by batching is '1' also note that the quality settings are set to 'Very Low'

or

1. Project window > Right-click > Create, or import four sprites > 2 sprite atlas
2. Pack sprites 1 and 2 to the first atlas & 3 and 4 to the second atlas
3. Drag all sprites from assets into Scene > play scene > game window > stats
4. Observe that the batches are '4' and saved by batching is '1'

Expected Result:
There should be 3 Batches (one for each sprite atlas and one for the camera) In this case, you should see "Batches: 3 Saved by batching: 2"

Note:
1. If an atlas have multiple pages, each page is drawn as a separate batch
2. If quality settings are set to fantastic an additional batch is observed for "ResolveAA call"

Also, the batching is getting affected if sprites position is changed in Z plane please refer Bug Case ID: 632743

Environment:
Occurring only on windows

Occurring with:
2018.1.0b1, 2017.3.0f3, 2017.2.1f1, 2017.1.2f1