Elon Musk has a special sense of humor, and he often said provocative things about cryptos before. It might be another joke of his, I don't know. Or perhaps he personally owns just 0.25 BTC but his relative/company owns way more... It could be that 0.25 is all he has, though. This guy is a typical trickster, IMO. Even now, saying that he owns only 0.25 BTC, he made the news because of telling Rowling that Bitcoin 'looks solid' in comparison with fiat, basically (see here). But in the same sentence he called bitcoin 'internet ghost money' which might be offensive. He keeps his crypto opinions well-balanced, so his neither a supporter nor an opposer in the end.