Can someone explain this drawcalls behavior ?

Hello,

I have a question about drawcalls.

In this scene, actually the ground is composed of many meshes (each 2 poly) and is actually not atlased. But the lightmappig is done and everything is set to static.

The static and dynamic batching are activated, and i have disactivate any light for testing purpose :

I have actually 54 drawcalls. If i hide all my floors tiles, which actually use 3 materials, 3 textures, are all statics with the same size 1:1, instead of gaining 3 draw calls, i go to 42 drawcalls, which is a gain of 12 ?

So, considering my lightmapping could be the reason, i disabled it and still have 54 drawcalls :

Does someone know how 3 materials using 3 textures, put on X static object lead to so many drawcalls ? Or i missed something ?

Thank you for your answer.