I assume the coworkers were talking about the practice talks, since we are as good judges of the real talks as the coworkers are, the talks being publicly available.

Or are you saying that they claimed he was nervous before the talks or backstage, but that the nerves went away once he stepped onstage? If so, why would he need to manipulate his coworkers into thinking he's nervous?

Or are you saying that he was nervous during the talks in a way that couldn't be captured by the cameras or the audience? In which case again - manipulation wouldn't have worked.

Or am I missing something?

EDIT: It seems I misread the original comment - he actually told the audience he was nervous. I'd love to know which product announcement that was and see it for myself. I'm still not sure how a coworker would be able to know what he was feeling any better than the audience did.