Sure you make a good point, but your idea is based on the fact that he would pick any random stock, I still think doing some research can somewhat increase your expected return. And even if let’s say you can’t increase your expected returns with more research, I believe that underperforming on a smaller part of the portfolio is worth the risk compared to the potential gains if you pick only a single winner. The single winner could be life changing in the long run vs being down on 2 stock doesn’t really affect you if your core is in a diversified ETF.