> if you fancy a potential career as a whitleblower,…
Most people don’t fancy a career as a whistleblower. They get their morals pushed further and further until they finally decide it is too much and they take the risk to their life and prosperity.
> it's much more credible and unassailable when the charge that the claims were made long after the fact for specific purposes is impossible.
If someone actually joined an org with plans to be a whistleblower I assume people complaining about whistleblowers trustworthiness would then be complaining that it was all lies because they always planned on leaking information.
>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.