This is from memory, but from what I remember, Google Groups doesn't allow you to edit moderated messages. Any editorial note would be a follow-up email.
That said, I'm not sure it was moderated, as looking onto the message source (this is still all based on email remember), there is no header saying it was approved, just that it passed through the list. This used to mean the person subscribed to the list, was given access to send messages (without having posted anything previously), and then posted the message. This is definitely very different to how this has been done in the past.
Note that I'm basing the above entirely on the lack of a header that usually denotes exactly WHO approved the message. It's possible Google has stopped adding that header (which is a pity, as it provided a way to figure out who approved a message to the list, etc).
Regardless of the above, I would suggest that if the policy is to change, even in a temporary/experimental way, that:
1. The list is notified of the change before or as it's made.
2. That the policies on the website are updated reasonably quickly to reflect the change.
This helps to avoid such confusion.