It does in some cases (see NASA X-57 where the fan is used to accelerate air over the wing, leading to a smaller wing with lower drag overall) but I'm not convi

It does in some cases (see NASA X-57 where the fan is used to accelerate air over the wing, leading to a smaller wing with lower drag overall) but I'm not convinced in this case. Having a system that is efficient at high airspeed and high thrust generally requires a variable geometry propeller (constant speed prop in GA terms) because a 'lift fan' at high relative airspeed, would have to spin much faster than a 'cruise fan' like you would see on a regular aircraft meaning airflow over the blades is higher leading to higher drag on the blade than necessary.