they don't know, the try and say the dc9 is smaller even though the majority of the remaing dc9s are -40,-50's now. Seat wise they are compareable to the 737s and the dc9 is the same type as the dc9-80. People talk about how"small" it is when they try and talk down about it but it's more compareable than they like to admit because then don't have the arguing points anymore with out the attempt to portray them as "small"
It's a pontless argument either way