To ensure SpriteShape can utilize SRP-Batcher, all Edge Sprites including Corner Sprites should be part of the same Texture in SpriteAtlas or a SpriteSheet.
In the given project, even though sprites are part of SpriteAtlas, there are two textures created due to not being able to fit all Sprites to a single Texture. This can be fixed easily either by
1. Increasing Max Texture Size of SpriteAtlas.
2. Removing Fill Texture from the SpriteAtlas as Fill texture does not need to be a Sprite and hence can be removed from the SpriteAtlas.
This should fix the issue. Previously in certain versions SpriteShape was incorrectly enabling SRP-Batcher even if multiple textures were used. This has been fixed recently.