Sync Attributes unsetting the Resolved By person

I recently added a new attribute to an existing work item type, and then did a "Synchronize Attributes" so that the attribute got pulled into existing work items (per a jazz.net article).

one of the owners of these work items said he had gotten notifications like this:

Susan M. Hanson <hansons> changed on May 31, 2012 at 2:23:17 AM United Kingdom Time:

Resolved By: Eric M. Covener --> Unassigned


You are receiving this mail because you are owner of this work item


So, why is adding a String type attribute and doing a Synchronize Attributes resetting (or Unsetting) the ResolvedBy person??

In the history, I see the same:
Resolved By Eric M. Covener Unassigned



Earlier this Month (1 item found)

Eric M. Covener May 11, 2012 9:08 PM
Status Under consideration Resolved
Resolution <none> Uncommitted Candidate
Resolved By Unassigned Eric M. Covener



I believe this is a bug, but I wanted to be sure.
Susan Hanson