RESOLUTION:
Based on the MNE the code, "Information update" is not something that MNE tool adds.
But it could still be related to migration that some MAPI properties caused Exchange
to update the meeting Subject line.
In the lab, we tested a meeting sample NSF file (also connected via CMN)
and when we made changes after migration to the meeting (instance or series)
in Outlook, we do not see Subject line change.