>If someone actually joined and org with plans to be a whistleblower

Yeah, I mean that's just espionage and should raise your standard of evidence for any claim made. The credibility of whistleblowers comes partly from the idea that they basically believe in the org's mission and were working sincerely to achieve it until they discovered information that they had a higher moral duty to report on. If they came in already believing it was illegitimate and their goal was to find dirt to expose, then you know they were already comfortable with one act of deception and you should consider that they might be comfortable with a second. It's the same heuristic that says not to take Project Veritas videos at face value.