If you set a Backup profile (one created as such to start with) to also delete orphans on Destination later, its Type will generally* become Mirror (specifically, 'Mirror Right'). The actions you configure set the Type.
Given you were talking about deletions being replicated, I assumed you had a Mirror profile (or equivalent - see below) already (because if you don't, it won't delete anything on Destination anyway).
* if you have any other settings that affect only one side (for example, settings to delete empty folders on Destination only), the Type may not change - because in that case, it potentially does not represent a Mirror (in the example given, because you have settings that may affect Destination without regard to Source). In this case, the Type will revert back to (or, not change from, depending when you set what options) 'Backup' (because it's not a true Mirror)
Given you were talking about deletions being replicated, I assumed you had a Mirror profile (or equivalent - see below) already (because if you don't, it won't delete anything on Destination anyway).
* if you have any other settings that affect only one side (for example, settings to delete empty folders on Destination only), the Type may not change - because in that case, it potentially does not represent a Mirror (in the example given, because you have settings that may affect Destination without regard to Source). In this case, the Type will revert back to (or, not change from, depending when you set what options) 'Backup' (because it's not a true Mirror)