This is a misunderstanding of the builder pattern. The whole purpose of the pattern is to decouple the building process from the concrete classes that are built. Let's have a second reading:
- The construction process must allow different representations for the object that's constructed.
This is not about having many constructors or not. The terms "construction process" and "object constructed" refer in fact to the "building process" and "the object being build". This is an English language ambiguity.
The key in that sentence is rather different representations. This means that the building process must be independent of the implementation of the classes involved, and should solely depend on their interfaces.
- The algorithm for creating a complex object should be independent of the parts that make up the object and how they're assembled.
Indeed, the independence implies in many OOP languages shifting of object creation process to another class. Theoretically, you could also think of a free-standing function in some languages, but in practice this would often not be sufficient.
The part about the assembling is key. THe idea is that the builder is used to construct complex objects. "Complex" means "made of many parts" (not to be confused with complicated, i.e. difficult to understand). So often you have to create the parts (sub-objects, components, ...), and then in the end "assemble the parts": this is often done by calling a constructor with the parts as parameters. Alternatively, it could also be done, constructing the final object, and invoke its interface to add its parts.
Caution: One frequent source of confusion is that there are two popular builder patterns: the GoF pattern (examined above) and Bloch's pattern (which is used in Java when constructors have many parameters). Unfortunately, the identical naming cause many people to believe it's the same pattern. There are quite a lot of blogs that pretend to explain GoF builder pattern, but with code corresponding to Bloch's pattern. There are also quite some that seem to think it's the same pattern and try to draw a mapping. These patterns are related, have some similarities, but are not the same and address different problems.