A free draining balcony is not to be confused with an open balcony, which has no soffits. Free draining balconies usually collect and transfer water to either spouts, or to the front of the balcony. The exception of this is using perforated soffits which are really a decorative solution only.
Previously, we found some clients choose to clad the underside of the balcony with decking to match the top surface. This would normally be in a free draining situation where water falls between the deck boards. This has become less common recently, as it doesn’t give the longevity of properly coated aluminium soffits and is often not a cost benefit despite having a lower perceived value.