I was listening to a podcast with Naval and David Deutsch yesterday. They talked about this. He said these kind of studies are kind of pointless. Yes. It's likely twins will more or less end up with same outcomes in life. Because they look the same and society has a tendency to treat people who look certain in certain way. But that does not mean what they can do in life is limited by their genes. What they think plays much more important role than their genes.
Humans are not born as mental "blank slates" that are completely formed by their upbringing.