We are discussing semantics. Is a pattern a Griffith's Gnat when peacock herl and grizzly hackle are not used? I fall on the side that a Griffith's Gnat is a very specific pattern.
There are several flies tied using palmered hackle with a peacock herl body. For example, a Renegade. I tie mine without the tag.
Like Flytire, I do tie variations on the Griffith's Gnat. One is a pattern tied Griffiths Gnat style using peacock herl but with a palmered black hackle. It works very well when small black midges are mating. But I would not tell someone I was using a Griffith's Gnat because to me that is a very specific pattern. Instead, I describe the pattern.
I suspect that Flytire's variation was for pale midges.
My view is that fly tied with foam would not be a Griffith's Gnat, but that is just an opinion.
There are variations of famous flies. The Lee Wulff's original Royal Wulff is the best example I can think of. There are Grizzy Wulffs, White Wulffs, Ausauble Wulffs, Adams Wulffs, Black Wulffs, Blonde Wulffs, Grey Wulffs, Montana Wulffs, and even a Were Wulff for fans of the Twilight Films.