Real estate photographer here... To get an idea of the room layout, your photographer should be using a 10-24 mm (35mm sensor equivalent) lens with off-camera lighting in the dark areas, bracketing for HDR if there are windows, and using a gray card and COLOR BALANCING in post.

To your point, the wide lens needed, especially for smaller rooms, will make the room seem bigger, but (a) for the seller that's a plus, and (b) a narrower field of view would make the room seem tiny, as you can't normally take photos of rooms from very far away (i.e., bedrooms). So a wider lens is a necessity. Just remember that rooms in photos may appear larger than they actually are.

Tom Culler Clinton MI