The problem is, DNT isn't just a Firefox thing, but something that the industry is attempting to adopt. So, DNT as a whole means something specific. It's a shame that there is that disconnect, but it's not a Mozilla specific problem.

Safari says even less about DNT (Ask websites not to track me) and the help isn't much better, though they have a separate section for blocking 3rd party cookies. But that's different from DNT.

This is a case where DNT as an industry standard means one thing to the industry, and one thing to the uneducated public. Damned if they do, damned if they don't.