Topher may not be able to follow his train of thought, but given how bad Johnny is at containing his emotions, he can follow some of the underlying emotions.

When the floor starts cracking, Topher calmly stands up. The chair disappears, and Topher walks towards the crack, observing it with calm detachment. "Is this your power, then? You can do this while awake, too?" he asks. It seems weirdly specific if he's able to manipulate the dreamspace in other ways.