Realizing you don't understand a subject as well as you thought you did and being either too proud or just not wanting to admitt to that has nothing to do with lacking confidence in Te IMO. I'm not even sure how you reached that conclusion.
Resistance to admitt to lack of knowledge during heated, on-the-spot intellectual discourse, especially if said person previously considered themselves quite knowledgeable on a particular subject, is exactly the type of behavior one would expect from EJ/Se-super id IME.
Some Si-EJs could just as easily compentently respond when being confronted on "Se" (though I'm not sure what you mean by that without specifics) without appearing to be cornered or as if they are projecting a fake image.