Why CmdBuf.DrawMeshInstanced doesn't update MaterialPropertyBlock changes?

Hello!
I have a command buffer which calls once (let’s say at start):
buf.DrawMeshInstanced(mesh, 0, mat, 0, arr, len, prop);

in Update i pass a float array to prop. But as I see buf doesn’t use updated array in it’s inner calculations during render process.
How should I make a command buffer to take into account the information which was updated in prop ?