I don't know why everyone is so upset about the NDA thing... It's such a standard business practice. Whenever I (a mid tier infra engineer at a mid sized software company) needed to talk to a vendor, get a product demo/consultation, get support on a licensed application, etc... We either sent an NDA to that company or bad one on file already with them. Nobody discusses internal processes, policies or roadmaps with an outside contact without an NDA first. It's literally just a standard business practice.
It could be nefarious, since it's meta afterall, but I wouldn't be shocked if there's thousands of people/companies who have standing NDAs with meta just so they could come on campus and demo their product to some team
I mean, the real answer is that most open source developers aren't here for freedom at any cost. They're here like a startup... Waiting to be acquired for big bucks. Open source doesn't pay bills, and if a megacorp pulls up in a Brinks truck full of cash, I wouldn't be surprised if 80% of open source projects sell