I do not think that Apple is taking it's own NDA seriously. It may just be there to be on the safe side. When Lion came out I had a look at some of the new API it had - while it still was under NDA. I had a couple of problems with the new API so I posted a request for help on G+. Some of Apple's own employees responded to my request.
This does not show that Apple as a company does not really care if you are publishing a very short comparison of one tiny tiny aspect of something that is still under NDA but I doubt they do.
I agree entirely that Apple's NDA is barely enforced. They don't put anything really special in the previews. They know anyone with $100 can see it, and that the rumor sites will get "emails from anonymous developers" with any interesting specifics not mentioned publicly by Apple.
(In fact, I read a theory somewhere that the NDA is really just about corporate competitive advantage for some legal reason. I forget what it was; it might have been something with the date a technology becomes public re: patent law.)
That said, more than almost anything else, I'd be wary about posting benchmarks. Performance is subject to change wildly between the developer betas and the final product. It could get better with optimizations and taking out debug code; it could get worse if some optimizations are found to be unstable.
If it was just, "Hey, this is awesome! They've implemented through OpenGL 4.1 and their implemenation is significantly faster across all OGL versions!" I'd be less worried. I can imagine a graphics programmer getting twitchy about early numbers.
People like John Gruber, who have close relationships to Apple and are - in theory - also under the same NDA openly talk about betas and previews on their blogs, podcasts and so on.
People like John Gruber have long been talking about unreleased software from Apple under the assumption that any information that is public is fair game (i.e. if you talk about something that you could have read on Macrumors there is no problem).
I’m not sure whether that would actually hold up legally – but that’s the theory.
(Also, Apple doesn’t seem to be very interested in actually stopping sites like Macrumors – which are filled to the brim with every tiny detail about the iOS and OS X DP – from actually publishing that. So I guess they are even less interested in going after people who do not even show videos or screenshots.)
It seems the have the NDA but if they actually don't want you to talk about something then they specifically tell you. For example when they demoed Lion I think it was to Gruber and a few select journalists they must have used something beyond the standard NDA.
As far as I understand, this NDA is used to make big newspapers publish reviews of the new OS at the same time to make a concentrate PR effort. If every big newspaper was free to review Mavericks, by the time it got out, no one would care about it. Also, early builds always have bugs and shortcomings and those will be discussed in the reviews. Using NDA Apple makes sure that major media sources release info on the latest, most tested version and at the same time to create necessary effect on the readers.
Those Apple employees should have pointed you to devforums.apple.com, which is the correct place to discuss NDA'd material. The fact that individual employees didn't is in no way indicative of Apple's official position regarding the NDA.
This does not show that Apple as a company does not really care if you are publishing a very short comparison of one tiny tiny aspect of something that is still under NDA but I doubt they do.
NDAs are overrated in general.