Like who? I've never heard anyone make such claims. All I've heard has been praise for Iommi.
Actually I once saw Van Halen...
Van Halen is pop-rock. Toni Iommi is heavy metal. You're comparing apples to oranges.
Iommi is OK but as usual, no one realizes Ritchie Blackmore gets stiffed and he is one of the pioneers of hard rock-Malmsteen basically admitted in the ‘80s that he copied him, scalloped fretboard and all. He never gets credit for basically inventing classicaly based rock.