I always thought he had a "grungy" (if by that you mean that more nasal, held-back) voice even in Armored Saint. Unfortunately I didn't note it on my autistic song rating list, but I know when I first heard Symbol of Salvation there were parts that sounded like early Alice in Chains to me. Even before that, iirc, perhaps as early as Delirious Nomad. fwiw the Sword guy sounds grungy to me too, particularly on Stoned Again. Fucking Axl Rose did that nasal thing. I think there's some common Aerosmith link between all of those. 3 of the big 4 of "grunge" are just hard rock/metal bands anyways, which makes the use of it as an insult particularly silly.
And your excuse makes no sense when considering that that particular song is track 5 and how he still only uses that voice for a portion of that song, I don't know how you couldn't recognize him. Stop listening to Metalucifer or something.