When ArchiCAD saves GDL object, it must place at the end of each script (apart of master script) END and all parameters of this object.
It is very easy to implement, but it opens great possibility to read parameters from another object using RETURN_PARAMETERS - without modifying saved object's script.
It can be useful for creating more complex objects with custom parts that are going to be used by people who are not using GDL at all.