Microsoft Teams will be available July 17 for the US Government Community Cloud (GCC)

Joel Markowitz You couldn't be more right about it being confusing.  My attempt to help you and others here isn't in an official capacity as a MSFT services employee, as which I am not myself privy to ALL the details of these processes.  This is why I encouraged you to leverage the contacts within your sales team as these are the folks with access to the Product Group - the only group - which can provide details of this nature, albeit through the conduit of your sales team.

That said, I deliberately chose the generalized term to refer to all parties involved in the audit and authorization processes which differ as you yourself note between GCC and DOD (I support both).   There being a difference between Box and Box's app for Teams, it has been explained at least in our circles that it is the app that requires audit and approval.  I myself have not tried contacting any of these vendors to see what kind of status they may have on those activities, but they would be the more appropriate party to direct the query to.  Microsoft will not be submitting Box or Salesforce apps for these processes as they do not own these apps.

I live your frustration with Teams GCC feature parity many times over every day as each of my customer faces the same challenges as you at the MTC.  I can tell you that the basic features like SharePoint Site Tabs are intended to be available in GCC in Q1, the goal being to bring basic feature parity (and this is certainly basic) to GCC.  Though 'feature parity' is a loaded term and not the best choice in my opinion.  The general restrictions of GCC on our SLG customers is a very real concern, and the account teams are actively looking for customers willing to offer this feedback so it can be taken to the product groups.  This is again why I encourage you to reach out through your account management channels as NDA considerations make it very difficult to paint a clear picture in an open forum such as this.

So as I said, I not only understand your frustration, I live it myself with the bonus of having to deliver the bad news.  If this sounds incomplete ("there must be more it") its because it is and as I have tried to suggest there are channels you can pursue that are less restrictive than this open forum.  I really do hope that this gives you some kind of path to get at least a little more specific information to help you and your org make progress on your implementation.  Happy holidays.