okay, so https://github.com/sonata-project/SonataAdminBundle/blob/master/DependencyInjection/Compiler/ExtensionCompilerPass.php#L103 is weird too (extends is strict extend but not the class itself, instanceof includes the class itself), but it has to be more complicated as you don't have a concrete class at that point - `instanceof` does not work on a string, so i guess the cases have to be handled with reflection. so i fear your suggestion above is the best we can do here.