It's widely presumed within faang-type-of companies that anything an employee says or does can be interpreted as an official company statement, especially by the press. As a result, many of these companies offer, often mandatory, trainings that underscore the importance of speaking carefully in public, since one's words can end up on the front page of a popular newspaper.
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.
