There is a difference between the actual LOGGING and then ARCHIVING/IMPORTING those logs into the database.
Logging will happen all the time, for all chats/users using a Sametime server. The inclusion/exclusion rules then determine which one of those logged chats will get archived/imported.
You could simply setup an inclusion rule which specifies a non-existant user to be required as a chat party. Since that user doesn't exist, the rule will always fail and therefore the log won't get imported.
Then, you could add another import rule which specifies an actual true filter (such as user needs to be found in a group, etc), and since that 2nd rule would then successfully pass, the chat would get imported. In other words, if you have multiple rules configured, only ONE of them need to 'match' for the import to happen (they are logically OR'ed... ie. Rule1 OR Rule2 OR Rule3).