A difference is the considerable rat-based theoretical/experimental justification for why it should work. Seth Roberts claims that he came up with the theory first and then invented the diet, which he then found to work for him.

Most alternative medicines/practices have clearly insane theory behind them. I don't know anything about nutrition, so I can't tell you whether it makes sense or not, but I can spot most pseudoscience a mile off.

That was enough to raise it out of the background lunacy. So I tried it and it seems to work for me. I couldn't agree more that a proper test is needed!