How does Unity Static batch handle submeshes

I have the following 2 meshes:

Mesh 1
Submesh 1 - Mat 1
Submesh 2 - Mat 2

Mesh 2
Submesh 3 - Mat 1 (same as mat1 from submesh 1)


Since submesh 1 and 3 have the same material and they are all static, I'd like to render submesh 1 and 3 in a single drawcall. However, Unity is failing to batch those submeshes together.

Is there a way to achieve this?