We've noticed that if you delete unlinked policies in designer, they are not recognized as changes when you go to deploy. As a result you can end up with a ton of Junk left up in the vault.
We typically don't unlink policies deliberately, but it happens.
Has this bug been reported yet?
So to duplicate, you would:
unlink a policy
deploy the driver
delete the unlinked policy
attempt to deploy (shows as equal)
If you then go to import, it will import the deleted unlinked policies back into Designer.