Yep that is true Kevin. Looks like it will be a delete and resave the new credentials so noone uses the incorrect one when adding a new device under SNMP v3.
On another side. On the Manage windows credentials page it list the number of nodes assigned to each set of credentials. Is there any easy way of getting a list of the nodes out of the DB. Just can't seem to find how the dbo.credential table links to anyother table to be able to get this info.