That's absurd. If someone submits evidence that "tone woods" make an audible difference, their evidence will be accepted on it's own merits. If, and only if, their is some reason to question the validity of their evidence, will credibility become an issue. You can say this person or that person is very credible, but without evidence, their claims and their credibility are of no interest. For example, the German guy who makes composite bass guitars and says wood doesn't matter without presenting evidence, without evidence, his credibility comes into play, and he has very little.Credibility bolsters ones ability to get people to view their “facts” as credible. Facts really are secondary to credibility in that way.
Suppose this was a murder case in a court room. If a witness says they saw something happen, their hear say is subject to a test of credibility. Are they believable? But if that person literally brings the murder weapon in and hands it to police, and it passes forensics, their credibility is neither here nor there. Belief becomes moot.