Where do group activities end?
At the gate or door of the meeting venue.
Anything inside the gate or door is a group activity. Anything outside the gate or door is not. Anything inside the gate or door is subject to Tradition V (primary purpose) and is subject to the supervision of the group conscience (including member conduct). Anything outside the gate or door is not to be labelled 'AA' and made subject to the supervision of the group conscience (including member conduct).
Why does this matter?
There must be a clear and firm boundary between a group and personal activity, so that people know, when they cross the threshold, they're entering into a bargain with the group. Yes, groups have very few (written) rules, but there are rules. Generally, no smoking during the meeting, no having sex during the meeting, no drinking on the venue, no playing the trumpet, no crosstalk, etc. If Sally punches Bobby on the nose at the venue, that's a group matter, and the group might implement its harassment policy. If Sally meets Bobby at a meeting and punches Bobby on the nose on their way for an ice cream sundae, that's an interpersonal matter between the individuals. Bobby can't complain to the group, and the group conscience has no jurisdiction.
Groups do not go for meals, hold picnics, and engage in other social events. Members of a group might do so, and a social secretary might announce such a meal or event as a courtesy to attendees and members, under announcements at the end. Strictly, there should be 'AA announcements' (for matters falling under the group conscience of the group or the supervision of the service structure) and 'other announcements' (relating to the venue or member activities that might be of interest, like a meditation or yoga session held by members of the group). But the group should never discuss, in a business meeting or group conscience, any other activities, such as where to go for dinner, or other social or spiritual endeavours of its members. In one healthy set-up I saw, the social secretary would announce at least one venue where members go for dinner or coffee, and invite other attendees to make similar announcements about where they were going, to maximise attendees' choice and opportunities for after the meeting. The more the merrier! Because dinner was not a group activity, there was no friction between the different groupings going to different venues, and the plurality was a bonus, not a bone of contention. The group and, by extension, the social secretary did not own the after-meeting activities of its attendees. The secretary might, as an individual, book a table at a restaurant, but that would be their own endeavour, not the group's. Others going elsewhere would pose no threat.
It's hard enough to keep group unity as it is, on purely group-related matters. One reason why the group's name should not be added to anything else is to avoid contention and preserve harmony. If discussion, vote, and substantial unanimity is not required, no agreement is necessary or possible, so no disagreement is possible, either.
Limiting the group's activities to what happens at the venue also means that anyone attending the venue for the meeting is a full member of the group simply by attending that meeting and being willing to serve. They don't have to join in other activities to be 'part of'. They're not missing out on anything. When the meeting is over and people go their joint or separate ways, they're doing that on their own account.
Lastly, safeguarding responsibilities stop at the gate or door. They do not intrude into the personal relationships between members, into sponsorship, into social activities, into the contents of Step Five, etc.
A clear application of Tradition V and Tradition V thus reinforces Tradition I (unity) and Tradition III (no conformity required).