Editing the group via the project browser opens it up outside the project environment. Essentially, the group is opened as a separate .rvt file. This is useful because it allows you to use the group in multiple projects. To get out of the group in this environment, just close it as you would close a project file, or save it as a .rvt file. After saving it, you can
"Load as Group" (under Insert Ribbon) and load the modified group into your project. In a perfect world, it would be nice to be able to load the group directly into the project.
In-place editing is where most people have had trouble closing the group, because of the Group tools ribbon floating somewhere off-screen when working in an upgraded project.