I don't think there's any redefinition here, and it's exactly this dichotomy that makes this a big issue. Vulnerability is indeed not "a good thing", but the issue is that the struggle to constantly keep yourself invulnerable at all times is a "worse thing", leading to many stress-related issues (amongst other problems). So the modern psychological advice, as I understand it, is to find particular people, spaces and opportunities where we can let our guard down, even at the risk of being open to attack, because the alternative is worse.

There's a stoic quote I love:

> our ideal wise man feels his troubles, but overcomes them

- Seneca, Moral letters to Lucilius/Letter 9 https://en.wikisource.org/wiki/Moral_letters_to_Lucilius/Let...

The way I see it, if you never let yourself be vulnerable, you can never fully feel your troubles, and you cannot fully overcome them.

My take is you've got the right reasoning but the wrong conclusion, I agree with your contextless definition of vulnerability and with the use of it in this context, vulnerability makes people vulnerable, by definition.

From my experience, the reason you'd risk being vulnerable is there are some things you can't achieve without doing so, it'd be like trying to do surgery with a scalpel on someone wearing platemail, or trying to detect radiation with a Geiger counter behind 20 meters of lead, for some tools to work properly they're required to be in a position where they're 'vulnerable', like eyes.

I think it's sad that performative emotions & vulnerability seem to be a popular thing to have to signal for acceptance. Which in my opinion is worse than nothing as at least when you're not faking something it's easier to agree that you haven't really tried it.