Owner manual "10.11.2 Editing members’ email addresses"
I would suggest to add a warning/note/blurb in that owner's manual section to the effect of "if a mod changes the email address in a group, the change affects all groups that member is subscribed to"
This is not documented anywhere (that I know of), and while many of the seasoned admins know it, apparently there are other owners/admins/mods out there (me included) who thought that when a mod changes a member's address in one group, the change took effect only for that group; in other words, similar to what the user would do if they wanted to do the same (change their address only for one group), by unsubscribing from the group, creating a new GIO account with the new address, and resubscribing with the new account to the group, the difference being if the user did it they would lose message ownership, join date, and such group membership info, whereas if a mod did it for the user within that group, GIO would "move" just that group's membership to the new account, in effect doing the same thing the user would have accomplished themselves but the message ownership and the like would be preserved in this case.
Hopefully this should make clear any unintended consequences/side effects of a mod changing the address.
See this thread for more info if needed: https://groups.io/g/Group_Help/topic/changing_a_group_io_member/77027138