It's kinda invalid logic you provided for exams. Because while it applies to the regular people, it doesn't apply to geniuses. And Nynaeve is one of the kind that Aes Sedai cannot afford to let her go. Nynaeve knows that. That gives her leeway.

As for breaking rules of the exam - while I agree that purpose of the test is to remain calm for almost all Aes Sedai, the true meaning of the test is to be able to channel under extreme duress. Which Nynaeve perfectly demonstrated. What she did is akin to taking exam on proving Pythagorean theorem and while doing so proved Ferma's theorem as well.

And the last thing, about what Cadsuane said and what Nynaeve did during the test. I think Nynaeve demonstrated exactly what Cadsuane said, because under extreme tests she managed to complete all the required weaves, but also she demonstrated her character doing much more outside the requirements.