I do not believe it is unreasonable to expect a consistent "Definition" of a FeatureSet and all language abide by that consistent definition.  An apple may be an apple in VB.net but you have to treat it like an Orange in Python......  In all other areas in the programming world I FULLY expect an object or class to return a a class/object that could be used in the same manner in any language or package.  That is a reasonable expectation!