There is no hider-expansionary dichotomy like you describe here. Hiding just means that the civilization is not exposing itself to outside threats by other more advanced civilizations, and is not detectable at our current level of technology. Hiding civilizations can expand, with whatever limitations the necessity of hiding requires.
The Dark Forest theory only tries to explain why our human civilization does not see obvious evidence of other intelligent civilizations.
There is no hider-expansionary dichotomy like you describe here. Hiding just means that the civilization is not exposing itself to outside threats by other more advanced civilizations, and is not detectable at our current level of technology. Hiding civilizations can expand, with whatever limitations the necessity of hiding requires.
The Dark Forest theory only tries to explain why our human civilization does not see obvious evidence of other intelligent civilizations.