I did say 'they are doing it' when you said 'similar' types. Regardless of seating, the B733/4/5 are definitely 'similar' types. There was no indication that you were referring to seating density in your post, in which case the aircraft type makes absolutely no difference, merely the seating arrangement. I completely understand your (now clarified) point however, and I can only imagine that kulula pax could end up on BA aircraft, but not vice versa.