I don't get the Berkshire Hathaway analogy. If you buy that stock, in what way are you not getting "1-to-1 direct exposure to the Berkshire portfolio"? You're owning the same investments Warren Buffet owns, in the same proportions, to within a rounding error.

It would be a mistake to invest in BH because, say, you're really bullish on Dairy Queen, but that doesn't seem like the mistake you're describing.