Hi Norbert, thanks for your additional comments and thoughts.

I think we agree that Warren Buffett is highly skilled at generating excess returns, but simply apply slightly different definitions to alpha. For example, if we would run a factor exposure analysis on RenTech's Medallion fund, then we would unlikely to be able to attribute the returns to common equity factors. However, in the case of BRK we measured structural factor exposure, therefore can explain the returns. Strictly speaking, the outperformance is not unexplained and does not represent alpha. Naturally this doesn't mean that it's easy to replicate what Warren Buffett has achieved. If you compare it to Formula One, we know the car, but it doesn't mean we can drive it like Lewis Hamilton.

We share most of your views on smart beta and have summarized some of these in the following piece, which might be of interest to you:
https://blogs.stage.cfainstitute.org/investor/2019/02/11/smart-beta-bro…