Secure List Maintenance and primary assignments

 Recently for an individual's record, the primary assignment was something that could be seen under a responsibility X.  I created a second assignment, then made that new assignment primary.  The new primary assignment falls under a separate security profile attached to responsibility "Y."  Without running Secure List Maintenance, the record can now be seen under the new responsibility Y and can not be seen under the original responsibility X.  In the past, responsibility Y could never see the record until secure list maintenance was completed.  If I reverse all the actions and make the original assignment primary again, neither responsibility X