Say you have a group of players as an attachment predicate with which you want to sync a value.
As soon as you add or remove a player from this they aren't notified of the current attachment state.
Having an option to manually synchronize an attachment for a Player would make it possible to fix this issue by synchronizing the attachment for said player after adding/removing from the group.
Additionally, it might be helpful to synchronize an attachment to a player with a specific value. As an example, if I wanted to sync the default value when removing an player from the group instead of the current value.