Our position
A function has a queue. A forum has an agenda.
The thing sold as a centre of excellence is usually a forum: interested people, a recurring invitation, and guidance nobody is obliged to follow. It fails in a recognisable way. Nobody is on call, so questions go to whoever answered last time. Nothing is written down, so the same entitlement question is re-decided three times with three answers. Attendance decays, the meeting is quietly dropped, and the work returns to whoever shouts loudest.
A function is the same people with three things added: a queue with a response target, a rota naming who is on it this week, and a decision log that is binding until somebody overturns it in writing. None of the three is sophisticated. All three are administrative, which is exactly why they get left out of a programme designed to look strategic.
We build this way ourselves, and the part we got wrong first was the decision log. Our own early rollouts had a rota before they had records, so the on-call person answered well and the answer evaporated. The second time the same question arrived it was answered differently, by the same team, in good faith. A log is not bureaucracy; it is the only thing that makes a rota compound instead of reset.