Are you saying that all current tenancies are below 80% market value? We've had plenty of FMs, in other threads, state that they actually worked in HA, or for the council, and there was definitely, definitely no subsidy on social housing.
Mind, we've also had FMs who say that they're in social housing, and can't afford private rentals in their areas.
How do we reconcile these two statements?
Private sector rental rates are irrelevant as to if social housing rents are subsidized.
Charging below market value for something is not subsidizing it.
Subsidizing it would mean paying money to reduce the cost.