That might be technically true, but most types of therapy seem to depend on some sort of theory of mind. Something like Cognitive Behavioral Therapy is based on the idea that thoughts can control emotions & behavior.
A p-zombie might change their behavior under any given therapy, but it may be more due to behavioral feedback, the degree of change may be lesser, without thoughts acting to multiply the change.
So therapies that focus more on just behavioral feedback might be overall more effective for people that don't have much thought in their head. Such as p-zombie challenged folks.