That's a contributor to the repo, not someone with commit access.
Although I don't know how FB rolls internally, it seems more likely than not to me, that it was ack'd by someone higher up in the organization than line engineers or managers. Someone with a permission of speaking publicly for a given area of a company - doesn't need to be CEO, more like a VP/Director maybe.
https://twitter.com/ylecun/status/1643945742850031616
https://twitter.com/ylecun/status/1644503237699969026
pretty clear the non-release and extremely half assed response to the leak is just CYA