I think most of the backgrounders in P90X went through the program, so their bodies are the results of doing the program (except for Dreya, who is a professional athlete/acrobate, and who was more cut to begin with).
I think Tony likes to use people who have actually been through te program, as he can point to them and say (as he does in the workouts) "X wasn't able to do this 3 months ago!" Since men have the advantage of testosterone and a faster metabolism, and build muscle more easily than women (and perhaps those who show up in the workouts were pretty cut already before starting P90X) it makes sense that they are more cut than the women (also, since men naturally have lower body fat than women).
I personally like the P90X backgrounders look, as it is something that is attainable for me (and that I find more attractive than a lower body fat, higher muscle % look).
It is true, though, that one's perceptions change depending on what they see all the time. I think when people get into weight training, and start reading the 'more muscular women' magazines and seeing those images, fit-yet-not-fitness-contestant-shape bodies start looking 'flabbier' than they would have if one didn't see so much of the uber-cut.
It goes the other way, too: people who see just the lumpy, fat average American (more than 60% of whom are overweight) look at the 'fit-yet-not-fitness-contestant-shape bodies' and think they are too muscular and 'gross.'
I think it's all a matter of perspective.