[2D][Sprite Atlas] Atlased sprites with different secondary texture order not batched in 2021.2

Note: Batching works fine for 2022.1 and 2022.2

Repro steps:
- Open attached project
- In Sprite Editor window, observe Axe_A has different secondary texture order than rest of weapon sprites
- Open SampleScene, enter playmode
- Open Frame Debugger, observe textures are referencing sprite atlas
- Observe 2-3 draw calls with Axe_A not being batched with rest of the sprites even if they are atlased

Expected result: Sprites are all batched together regardless of secondary texture order when included in Sprite Atlas
Actual result: Sprites are not batched together due to secondary texture order even when included in Sprite Atlas