It seems there is some number behind the hood. That splits statistically batched object to multiple draw calls. Inspector shows that all the objects are combined (But I'm not sure if unity shows real combined mesh)

Project Steps:
1. Open the 'test' scene;
2. Run game, the draw call is 1;
3. Active the 'TestMesh(5)', then run game, the draw call is 2;
4. Please note, there are no any lights, and disable realtime shadow on quality setting