In the 4.2 migration commit protocol, this simply makes the donor keep trying to refresh (while it is not shutting down), instead of giving up on refreshing and marking its filtering metadata as UNSHARDED.

In the 4.4 migration commit protocol, the results of this refresh will be guaranteed to reflect whether the migration commit succeeded or failed, making it possible for the donor to inform either itself or the recipient to go ahead and delete the orphaned range.