I agree that it is possible that Buffett may have Bitcoin all the time while speaking against, we can't know that. Somehow it doesn’t seem realistic to me that he and the people around him could successfully hide it for so many years. If he invested directly in BTC, he bought it through the OTC of some famous CEX (probably Coinbase) who then keeps it for him - but for people who have so much money it is certainly not difficult to hide the connections that lead to them.
This is why I believe that there is a strong possibility that he and people like him already own a lot of bitcoin without letting anybody know.
I don't know if WB has had any scandals in his life, but it seems to me that he cares about maintaining his reputation, even after he is no longer alive. His view is that he will leave only 1% of his wealth to his children and donate the rest to charity, although some would say it is a bit hypocritical given that he has set up a $2 billion foundation for each of them