My problem with that explanation is that @StealthMountain and @DBZNappa both only ever tweet the same message, and to my knowledge both have been running for quite a while.
Anyway, in my research, those are some of the things I found, but I don't have citations. I think the @replies are the more important half of things, and I imagine those bigger ones get a pass because they're so popular.
Also has to send some non-@replies, so it'd work better as a dual-purpose bot that does some other work too, I guess.