Imagine someone who has locked the front door but left every window wide open. That is the person described here. The hands and feet are still. The body looks disciplined. But inside, the mind is feasting on every sense pleasure it can recall or imagine.
Krishna uses a sharp word for this: mithyachara, one whose conduct is false. When the outside does not match the inside, the entire exercise becomes a performance. Real spiritual practice requires alignment. What you do with your body and what you do with your mind must point in the same direction.