It is true that our Discourse groups generally map to a single category, if that’s what you mean.
Even though some headway has been made, group messaging is still confusing as heck for our users 
There’s currently no one place where someone can go and see all their messages, as I noted here:
There are other issues with groups – but the short of it as that using categories requires more finagling on my end, as the admin, but is more understandable for users.
Here’s how I’ve worked around the permissions issue:
The link takes you to the group’s page, which allows you to view its membership.