Lots of people from various forums have built this with my PCB and found it to work (I of course have too). I believe most people who build this bypass any info from TG completely and go straight to the GEP article that Chris Carter built his from. Roy Gwinn, who is a member here, is the designer, not Chris Carter, and though I'm no TG fan and don't know much of their history, I would assume he built it straight from the article.
I mean no offense to those guys, but I don't imagine they knew or cared much about electrical engineering, just like most musicians, so I wouldn't put too much stock in any grandiose claims of their "inventions". I don't think they did anything to this circuit but name it and make it popular (by the standards of industrial noise effects, anyway).