For me the statistical (volatility) data is more an argument of having at least some amount of stocks to smoothen volatility – unless you’re Charlie Munger[CM] – and not necessarily an argument to limit yourself to x number of companies but not more. Peter Lynch used to have hundreds of companies in his portfolio.
Maybe I want to have more stocks, but I’m not motivated by less volality. If I have, say … (checks stockpicking portfolio) … 96 companies in my portfolio and I come across something else that I potentially find interesting, why not add it to the portfolio once I’m convinced it’s a good investment?
YMMV, of course (especially if you’re Charlie).
CM “The whole secret of investment is to find places where it’s safe and wise to non-diversify. It’s just that simple. Diversification is for the know-nothing investor ; it’s not for the professional.”
— Charlie Munger