Maybe they distinguish it because ADs can make some people manic and they're saying the advertised medication is specifically designed to bypass this trait of other medications?

Ultimately I don't think there is a difference between MDD and BP depression, but maybe there is, I don't know, I'm not a psychiatrist/psychologist.

And yes, it may very well just be a marketing scheme. I always find it odd that they advertise ADs ad APs on TV. I'm more willing to ask a doc about medication I hear about from my peers (you wonderful people) than meds I hear about on TV, because the TV spots are put out by pharmaceutical companies trying to push pills as opposed to patients who have actually tried the medication.