Generally speaking, you can't really tell what someone knows based on their words or actions.

Performative behavior is not a modern phenomenon. Deceitfulness is so effective we're not going to end it by discussing Dunning-Kruger every chance we get. Mere knowledge is not enough to defeat it, and you'll always be sorry when you underestimate your opponents.

It's all ultimately a matter of trust, and that takes time most people don't have or don't want to give. It's more important to stack incentives to compel behavior and hedge your bets against people who seem off.