Both types of NDA exist as far as I know. What you're saying is true Catbus, but on the other hand F(x)tec could also see the beta test phase as a way to kill two birds with one stone: getting feedback from beta testers about NDA stuff, while letting them show non critical pictures or situations to get some extra coverage in social media and slowly let the hype escalate.
For instance, it seems that people who attended the event in Germany were invited to mention the Pro1 to friends on social media, in exchange of getting their device a few days before release.
No idea what is best, I'm just curious.