What they probably mean is the passing of the torch. Black Sabbath passed it to Judas Priest, they passed it to Iron Maiden, it got stolen by Glam Metal, the Big Four of Thrash reclaimed it, they passed it onto Pantera, then when they broke up the torch got lost somewhere. Then metalcore stole it. Now that Thrash is reclaiming it again there's metalcore trying to keep it by "going thrash." I have absolutley no clue where I'm going with this, at all. ... Nope, still no clue.