Okay, good to know that that's the way it is designed.
However, using 'mgr' context for manager pages does pose some problems.
For instance, we are using the filemanager_* context settings so that each context gets its own private directory for static files.
If we make a user an administrator of a context, and they log into the manager, they will lose these settings and see the whole file tree.
A grey area is the modx file browser. It lives under: '
http://foo.example.com/connectors/browser/directory.php?action=getList', and gets put in the 'mgr' context by the connector entry script.
So even if you launch the filebrowser from a frontend context, you end up in the 'mgr' context, and you lose all your context-specific filemanager_* settings, and you get to browse the whole.
Maybe this is all just a specific problem with the filebrowser system. But I wonder if there are other context settings that you would want an administrator of a context to retain when they log into the manager?