Its such a contradictary thing for malmy when he says single coils = articulate, and then he turns all his marshalls to 11 and uses a DOD pedal (all knobs to 11) and then uses 2 x NS-2 pedals (or has he upgraded to ISP decimators?) to get the level of gain he wants. His tone is uber compressed: what dynamics/articulation?
Also, yeah, its true, low output pups with hi gain pedals/amps = metal tones or heavy stuff. On the other hand, penta, you would also note, humbuckers = more compressed tones. Thats one of the reasons metal players prefer hi output pups, though, as what you said, not necessary. The compression aids in getting more body in power chords and increasing overal chunk/chug. Plus bass helps.
While I agree with you that single coils = aritculate and you should NEVER compromise on your root tone, I personally cannot get used to a single coil in the bridge. Too thin, un-naturally tight and little bass. I don't care who uses single coils for metal, but it ain't working for me.
Also, if you eq your gear to suit your bridge single, more mids/bass/body, your neck single suffers from excess flab: bane of strat owners for ages. Anyway, single coils in the neck @ the 24th fret sweet spot = excellent tones. I do wish my Saber was H-S-S. FGM400 anyone?