I was thinking of the parameter passing aspect of PL/SQL (from 7+), not the constructor aspect they added in later on.
You're quite correct also, that I'm thinking of overload rather than polymorphism. I had also switched from Oracle to Java (because I still don't think of PL/SQL as OO language).
I'm not sure that a static factory method would be required in this case for Java, if the constructor can be overloaded to default the values.