Being the cool wife is not saying anything when your dh is doing something that makes you feel uncomfortable, for fear of being accused of being clingy or insecure.
And yes, if you minimise someone else's insecurities then you are pushing the "cool wife agenda".
We're all different and have our boundaries in different places. The cool wife will push her boundaries and quash her feelings for the sake of being seen as "cool".
So if you are happy with your dh going on holiday with a female friend, then you're not a cool wife. But if you criticised someone else for not being happy with it, then you're projecting the need to be a cool wife on someone. And that's not fair.
Even if you don't agree that the worry is a valid one, if someone has a worry the sensible thing would be to encourage them to communicate that worry in a calm way, to get some reassurance from their dh. A cool wife worries alone and doesn't share her fears. That's not how love should be.
I remember being the "cool gf" when I was young. But then I grew up and realised that my needs were valid, and my discomfort was justified. Being the cool gf, just meant I put up with shitty behaviour, when I should have been treated with respect.
So there you go, a cool wife is either squashing her true feelings due to fear, or not empathising with those who are struggling with what to do with those feelings.
I am happy for dh to have female friends, go out to dinner with female colleagues, go out without me without me contacting him, this doesn't make me a cool wife. It makes me lucky enough to be in a relationship where we trust each other.