Air con is short for air conditioning, not air cooling.
Part of the process dries the air as it comes through the dash ventilation system so on a damp day when you turn on the A/C to clear the windscreen you are blasting dry air on to it.
As a convertible is inherently damper than a traditional tin top it is more likely to have condensation on the windscreen on a cold morning.
The system on the MGF also adds a second cooling fan and both fans can be switched on by turning on the air con, ok, the air you draw through the radiator is warmed by the air passing through the A/C condenser but you do get a way of turning them on in an emergency.
On a hot day in southern Europe it is great to turn it on and pump cold air at your feet or face.
It is a satisfying DIY project to complete.
Home to black Alfa Romeo 159 3.2 V6 Q4 ,green MGF VVC and red MG Maestro T16.
MG - the friendly marque.