You're welcome!
I agree that MS has done a miserable job of documenting bits like this. I didn't
find out what the content controls Group command was for until nearly a year
after I first saw it, when one of the development team demonstrated it. Before
that, I'd seen another MS demonstration that involved surrounding the entire
document with a rich text content control and turning on its "contents cannot be
edited" option; the content controls embedded within it will continue to accept
editing. That works, but Group is easier. And yes, the name is misleading.
To protect any content control from being deleted, select the control, click the
Properties button in the Controls group, and check the "Content control cannot
be deleted" option. You'll also find that once the document is grouped, content
controls can't be dragged away from their original positions.