I admire the way in which Elon Musk thinks and the innovative ideas he has, i really do think he is saying the truth about the amount of coins he is holding as there is no point for him to lie about his investment in BTCitcoin. 

The reason is he is a self made billionaire and he is not an investor, he made his billions through his inventions and he is pretty damn good at that and if he says that he just is holding 0.25BTC just to check what is all about, i believe what he is telling. He is an individual who is planning to sell all of his possessions including his luxury mansions and wanted to rent a modest place to live. It is weird but that is Elon Musk.