incline bench is more dominate then flat bench
I know and I'm sure the guy in that picture knows this as well. I always had a good line on my lower pecs until I decided I wanted to do heavy flat bench for a couple years. Now, that I've gone back to inclines, my pecs are hanging down a little. That is why I don't think it is genetic, because it never happened to me until I started doing heavy flat bench presses.
So besides inclines and dips, that's about it? No secret thing I'm not aware of? Maybe if I stick with inclines my lower pecs will atrophy enough to not be a problem.