Builder Pattern : Can our director deal with Concrete builders directly?

I was reading builder design pattern and have the following doubt - Why director cannot accept the concrete builder type reference ?

Suppose, we have a CarBuilder interface which implemented by 2 concrete builders SUVCarBuilder and SportsCarBuilder . We see that our Director class is like -

public class Director {

    public void constructSportsCar(Builder builder) {
        builder.setCarType(CarType.SPORTS_CAR);
        builder.setSeats(2);
        builder.setEngine(new Engine(3.0, 0));
        builder.setTransmission(Transmission.SEMI_AUTOMATIC);
        builder.setTripComputer(new TripComputer());
        builder.setGPSNavigator(new GPSNavigator());
    }

    public void constructSUV(Builder builder) {
        builder.setCarType(CarType.SUV);
        builder.setSeats(4);
        builder.setEngine(new Engine(2.5, 0));
        builder.setTransmission(Transmission.MANUAL);
        builder.setGPSNavigator(new GPSNavigator());
    }
}

The methods accept Builder type rather than concrete types - SUVCarBuilder and SportsCarBuilder. Can our director not accept ConcreteBuilders types ? That way, we can even return the concrete product from director itself.

public class Director {

    public SportsCar constructSportsCar(SportsCarBuilder builder) {
        builder.setCarType(CarType.SPORTS_CAR);
        builder.setSeats(2);
        builder.setEngine(new Engine(3.0, 0));
        builder.setTransmission(Transmission.SEMI_AUTOMATIC);
        builder.setTripComputer(new TripComputer());
        builder.setGPSNavigator(new GPSNavigator());
        // Get the concrete product
        return builder.getSportsCar();
    }

    public SUVCar constructSUV(SUVCarBuilder builder) {
        builder.setCarType(CarType.SUV);
        builder.setSeats(4);
        builder.setEngine(new Engine(2.5, 0));
        builder.setTransmission(Transmission.MANUAL);
        builder.setGPSNavigator(new GPSNavigator());
        // Get the concrete product
        return builder.getSUVCar();
    }
}