I'm reasonably certain that OpenBSD has never agreed to any NDA from anyone as a matter of principle. It's one of the things that makes me love the project so much.
I don't know if "never" is accurate, but certainly they are very NDA-averse. That's their right, but it means they're going to get left out of things like this; it's simply not possible to organize coordinated disclosure of issues if the participants don't agree to not blab ahead of the agreed disclosure date.
An NDA is a legal agreement. It's entirely possible to organise coordinated disclosures without a legal agreement. The folks pushing NDAs, however, don't seem to be interested in other sorts of agreements.
The alternative would be a "gentleman's agreement"? An NDA would seem to be much more transparent with everyone understanding what was agreed to rather than something agreed upon over cigars and cognac. Refusing to sign NDAs as a matter of principal doesn't seem like a very mature way to conduct business.
To be clear, we do routinely operate on the basis of "gentlemen's agreements"... but Intel is a corporation full of lawyers, so I would be astonished if they were willing to work on that basis.
It doesn't have to be a handshake and a nod. Things can still be clearly written down. But formal contracts with consequences take it up a notch. And this isn't about how you "conduct business"; that's a very business-oriented view of what's going on.