Jazz players ( i have to agree) are usually very well versed in scales and modes.....BUT, that doesnt mean that one cannot 'shred' better if they knew those same things. Ive been a guitarist most my life but wasnt until recently too versed in modes and some music theory. It turned out to be the missing ingredient. Take a Jazz player and make him into a hard rocker and watch out for the best shredder youve ever seen. (personally i hate jazz)