PST migration policy vs. Mailbox policy

Our PST migration policy is set to archive all message classes.  I checked the log file after migration and it showed a number of items not elgible for archiving because of PST migration policy setting.   All those items are calendar items which are included in the PST policy.  However, our regular mailbox policy does not archive calendar items.  Does it means regular mailbox policy overrides PST migration policy?

Also, we set it to delete PST file after migration.  The PST is not being deleted and the migration status stays as completing.  Is it because of the non-eligble items?  Any way to fix that?

Thanks.