As discussed in today's daily meeting.

When we register for updates with SMMR controller, we immediately get a first push containing only the control plane. After that we get another push with all SMMR members + control plane.

In my scenario, the SMMR is already "ready" with some configuredMembers already in it. I'm not touching it in any way. I'm just registering for updates and getting two pushes as a result.