joining the larger thing
The word Group in AA Group is always capitalized because Boston AA places enormous emphasis on joining a Group and identifying yourself as a member of this larger thing, the Group.
Context
The typography as doctrine: Group capitalized because Boston AA's whole cure runs on subordinating the isolated self to "this larger thing, the Group" — the identification with the collective that the disease of self-will most resists. Likewise Commitment, Giving It Away — the capital letters marking the load-bearing terms.