It's simple, think of the vocals as an instrument. If you are writing dark sounding metal (take doom metal for example...), it isn't gonna sound too appropriate having Bruce Dickinson wailing away on the songs that are supposed to sound depressing, is it? Vocals are an instrument, as much as guitar, drums, bass, and keyboards, and they are used the same way. Thanks my opinion anyway.
Back on the topic, I don't think I believe that those quotes are real. It just doesn't sound like the way the Metallica boys would talk IMO, though I may be wrong, and even if they are true, comparing the new material to stuff like Meshuggah doesn't mean it will sound anything like them...
Also, Bob Rock has been playing bass in the studio, and will play on the album. He also played at a secret gig they did a couple of months back, but it has been said that he won't tour with them, so they will probably just hire someone to stand to the side of the stage and play, I guess.
I eagerly await new Metallica.
