When you extend the type into a new type the Factory function (Create, whatever) is also present in the new type. Then, it only returns an object of the previous type, and since it can't be overridden, you have to create a new Factory function with a different name. Even though you will never use the old 'Create' function again, it is still there. Code Bloat
If I have a function that relies on factories and needs arguments specific to a specific factory, then I put the arguments in a bank and pass them.
That way the factory in specific gets its information from the Url by casting to a TBank and checking to see if it's not Null, and all the other factories ignore it unless it's the correct input.
Just my 2 cents.