I notice there is next to no reinforcing material inside these walls, which seems very unwise. This guy might be printing more visually impressive rooms, but they seems a bit less stable than the ones being printed in China. Is the sparse rebar in the first image really enough reinforcement for a wall?

Also, I notice some overhangs, which is impressive, I wonder how much overhang this concrete is capable of. (Looks like about half an inch per layer?)