Not sure I totally agree. You can still have say two unrelated people sharing a room (x2). So for example a 1 bed flat with 2 people in the living room and 2 people in the bedroom; or a Studio flat with all 4 people in one room. I see where it comes from though, and I guess including them in the definition but not licensing allows them to magically decide to licence 3-4 HMOs on very short notice.