chests today are bigger then teh use to be. Its the comparitive effect of the rest of the body being bigger as well. Ronnie had a massive chest, ruhl,dj, branch, victor has a very thick chest.
Has nothing to do with stretch, as i have no idea why that would change the origin and insertion of the pecs or number of fibers. Training style has nothing to do with shape of the muscle, its genetically determined. My biceps are high, nothing i do will make them look like olivia's