Probably on the fact that FB will surely publish its business report for Q1, and he uses it for his PR, whether he has any information that it is true or not. I read some of the comments below his post, and in some of them some mention that he already had similar rumors that proved inaccurate.
I guess, but then this should be for most major cash-heavy companies. But yea, I guess mentioning a specific company will get you more publicity.
Still, I wouldn't be surprised if FB really announces that it has Bitcoin in its possession, when it comes to profits, companies like this don't choose ways - selling user data, Libra or Bitcoin doesn't matter.
This will really really be an interesting few weeks for sure. There were also "rumours" about Apple, and their earnings report comes tomorrow(2021-04-28). *fingers crossed*