From my perspective, that Wired article was really just tongue-in-cheek, and was not at all seriously saying GTD is cultlike, in the sense of a real cult.
It isn't.
But one could make a very strong argument that it is something used by folks who can have quite Obsessive personalities. It can easily be taken to the extreme, when people go berserk with their lists.
David Allen and his people do market his personality, as personality marketing is what works with most people. Even Geeks go in for that, as its human nature. But DA is doing this in a pretty limited way compared to many other folks out there.
Personally, I don't put his work in the same category as these so-called bogus "success and self-help gurus" who use the techniques of personality marketing to the extreme.
GTD is not a cult, or even cultlike.
But as an off-topic aside, in terms of a REAL cult, a GTD-like comprehensive system for "controlling your life" could be used as a mechanism to control people. So it could be abused. So there is some truth that this type of obsessive system for total life control, could be easily used in a nefarious way. I could give a couple of examples right now where people are doing something along these lines....
I hope DA continues to stay out of the flakey "self-help" business, and just sticks to teaching his system, with minimal show-biz frills. I guess it all depends on which direction he wants to take it.