I would agree with you if they did not use established standards of polling that renders the polled individual anonymous and if groups such as Rasmussen and other very reputable sites were not repeating the same results.
The nominee can choose not to answer questions.
The committee members often give long winded speeches then either serve up softball questions or go into attack mode, depending on whose party the president belongs too.
Nothing of substance is learned about the nominee other than what already can...