I heard Skinner tell a guy that "behavior" includes the physical environment/body and thoughts. That these things can't be separated.

He was essentially just a fatalistic that believed in hard determinism.

He didn't really think you could change behavior via free will because free will doesn't exist and the entity doing the conditioning had no free will either. As such both the experimentor and the experiment have no free will. They are destined by physics to do what they do.

All we actually do then is deterministically reflect and introspect on our determined reality.

There is nothing to change or do. We are just watching life go by internally precisely because we have memories of previous moments. It's also precisely why we are able to create models to predict simple futur le events like how far a ball will be throw. In a gravitational field giving an initial acceleration in a vacuum.

Why is he just known as the guy who taught dogs to slobber with bells? He was trying to illustrate that we are all mechanical automatons.