This is bullshit. I have never listened to any terrible popular core band to get into metal, in fact, even when I just started listening listening to metal I thought all that shit sounded gay as fuck.
Your reading comprehension blows, dude. I said, twice, in that post that it's not a universal rule and yet here you are, going "NUH UH I DIDN'T DO THAT." Hey, congratulations. You're like a guy that walks through a minefield without dying telling all the dudes missing legs that minefields aren't dangerous.
Also, how old were you when the -core bands hit? I'm assuming you weren't 14 years old when Job for a Cowboy and Whitechapel hit it big (or maybe you were). The point is that "radio metal", whatever incarnation, tends to market REALLY well to disaffected teenagers.
I'm speaking out of friggin' experience here. I was a counselor for teenage boys with anger problems for about two years and so many of 'em had their Asking Alexandra, Bring me the Horizon, and Bullet for my Valentine shirts, and then we'd get talking music and they were interested in heavier stuff, so I made suggestions and then next thing you know they're raving about Suffocation or Goatwhore.
Maybe for YOU it was AC/DC, but how did you hear AC/DC? They aren't on the radio. They aren't blowing up YouTube. Obviously someone had to show em to you. For me, my first real metal was Dio and Priest because my stepdad had an old suitcase full of classic tapes but that sure ain't the usual.
TL;DR learn to read