Why does the builder pattern not have a method `GetResult()` in the builder interface?

From Design Pattern by Gang of Four,

Example:

Why doesn't the interface Builder have a method GetResult(), which is overridden in the concrete class ConcreteBuilder?

In the example, the concrete builders have GetXXX() methods, where XXX is different for different concrete builders, which doesn't promote "programming to interface" at all.

Is this "omission" deliberate in the builder pattern?

Thanks.