Now, there is nothing wrong with ScrumMasters getting together to discuss obstacles, process related topics, and new tools/techniques for improving. The early large implementations of Scrum mostly referred to these as the ScrumMaster community. I strongly encourage that approach to shared learning for any group of people in a specific discipline.
I believe that this trend is nothing more than a form of control from people in ScrumMaster roles that used to be project managers. Information power...having info that others don't, is a form of control. It's time to let go folks! It's OK, nothing will happen, everyone will be fine. Smart working adults will learn to coordinate their activities just fine. My suggestion is to get focused on the obstacles that nobody wants to deal with or find ways to improve the process or the development environment.