I don't own either, Armalite or DPMS, I don't have a dog in the brand superiority fight.
With regards to the online vendors who mislabel their wares, they have to deal with the dissatisfied customers, returns, and liabilities of misinforming folks.
Just because enough idiots are doing it doesn't mean it should be mainstream, or that it's not insensible. If anything is childish, it's an "everyone else does it so it must be OK" mindset.
People that get screwed over by online vendors don't generally go back to them for help, they come here to get information. If they get here and run into the same ambiguity and confusion, we've done them a disservice.
That's where I'm coming from, and to quote Forrest Gump, "That's all I have to say about that."