There is nothing wrong here! It's his personal choice not to hold Bitcoin! Most of the famous billionaire doesn’t hold much Bitcoin, maybe their thoughts are different, I am not surprised at all! Recently J.K. Rowling tweeted her curious about Bitcoin and later she received some awful comment, after that, I don't think she will buy Bitcoin now, maybe later! So, it's normal, not surprising news.
But maybe Elon Musk is just tripping where he is not telling the truth after all. It will cause a massive hype all over the internet if he will reveal the true numbers of the bitcoin he holds. I'm sure that he is now also accumulating bitcoin, he is a billionaire after all and I know that his tweet is not true.
Observe the tweets of Elon Musk, he is talking about bitcoin in the past weeks and months. I know what Binance said was true, expect a billionaire like him that he also holds a lot of bitcoin.