This is kind of a corollary to the issues with rejecting conspiracies - when we reject a supposed conspiracy, due to lack of evidence, that can easily come across as claiming the conspiratorial claim is outright false - but in a sea of such claims, some then turn out to have at least a kernel of truth, which then turns into a big gotcha moment: "see, they're repressing us, we were right all along!"

So while I understand the idea of maintaining trust by not backing anything uncertain, I'm not sure it's the right call. Maybe communicating that uncertainty is better, and even communicating hints and possibilities - instead of trying to control the narrative but thereby ceding the ground to nutjobs until certainty arrives, often granting them considerable prestige if they guess sort of correctly ahead of time.

But that's already happened with vaccines. A bit late to worry about that now.