Why does Abstract Factory deal with families, and Factory Method with generating a single object?

From what I have read, the abstract factory pattern typically concerns itself with creating several objects which are all associated with the same family, and the factory method pattern concerns itself with generating a single object.

Consider the following example, which flips those concerns:

// Factory Method (base class) allowing for creation of families of objects
public class BasePizzaCreator{
    abstract ISauce CreateSauce();
    abstract IToppings CreateToppings();
    abstract ICrust CreateCrust();
}

// Abstract Factory (interface) defining contract to create a single object
public interface IPizzaFactory{
    abstract IPizza CreatePizza();
}

It is obvious that you can use them this way - but is it a violation of the spirit of the patterns? If so, why?

What I really want to understand here is this: Why is Abstract Factory the better approach for creating families of related objects, and Factory method the better approach to creating a single object?