Sound Debate 

If Machine Head are to be classed by a certain sub-genre of metal, two things really need to happen: 
1. There has to be a rationale for the classification in the 'Sound Debate' sub-section. They've been considered for about 10 different metal genres at different times, so this can't be stressed enough.
2. If there is to be a rationale, some form of substantiation would most definitely help. Either a recognised critical opinion or perhaps even the band's own thoughts. Encyclopaedia's aren't meant to reflect one person's particular opinion.