[foerbert]

I'm not sure about that.

It certainly could, but it also certainly couldn't. I imagine being confidently incorrect is likely to produce a worse result than being unconfidently(?) incorrect, for example.

Similarly, a less confident speaker may end up spending more effort justifying their answers, which could better expose their knowledge.

I think it would depend quite a bit on the examiner in this case. Some people may even be simply biased against particularly confident speakers, particularly considering the relative positions of the speaker and examiner.