From context they mean pretending to be a legitimate law-abiding telemarketer who plans to use the do not call list for screening purposes when in fact they are an overseas telemarketer who plans to use the list as a cheap set of known working phone numbers.

If you have a policy of never giving these people the time of day, then it's no different

If you're the sort of person that is too polite to just hang up and you might get hooked by a scam caller because you let them talk to you, then it's a big difference