They also used a Flextone or something didn't they? I think I can hear more than a hint of Line6 in The Blackening.
Actually, one time I had a guitar tone worked up, a guy came round, he said it was just like "Burn My Eyes" so we put the CD on and compared, it was barely even similar.
If a guy says he wants to sound "like Machine Head", perhaps sometimes the tone he has in mind doesn't actually resemble any recorded Machine Head tone too closely...