My experience as a team lead working with a lot of juniors is that they are terrified of losing face

So much this! Both from my experience as Junior very many years ago and also with Juniors (and not so Juniors) today.

    tend to talk a big game

Very big game. Claude does too. The kind of BS it spews in very confident language is amazing.

    As a team lead, I try to use language which expresses any doubts or knowledge gaps I have so that others in my team feel comfortable doing it as well

Agree. I also often literally say "Dumb idea: X" to try and suss out areas that may have been left by the wayside and under-explored or where assumptions have been made without verifying them. It's amazing how often even "Seniors"+ will spew assumptions as fact without verification. It's very annoying actually.

    superpower

How do you actually do this tho? I would love to do this but it seems hard to find an actual "superpower". Like where does "super" power start vs. "yeah they're better at this than others but definitely not as good as me or "person X that definitely does have that superpower". Like when can you start encouraging so to speak,