That might be ideal but it's completely unrealistic. If you haven't worked through it with a therapist, then you'll very likely end up losing emotional control if you open up about it. Working through it is what allows you to let them know what's going on and what you're going through without having an emotional break down on them.

If you've worked through it enough where you can talk about it with them without losing control over your emotions, then it's fine to tell them.

The reality is that it's not the vulnerability aspect that is off putting for women, it's the loss of emotional control that comes from not dealing with that vulnerability at all. That sort of loss of emotional control is really only going to be seen as acceptable in the immediate aftermath of trauma/loss/grief/etc. Losing control in any other situation gets seen as the person having a weak control over their emotional state.

For many women, this plays a role in attraction. A man in control is going to be desirable. The opposite of a man in control is a man with a lack of control. Who is another group that has a total lack of control? Children. And that's where man-child came from. The guy legit starts to get treated like a child instead of a romantic partner.

The guys saying never be vulnerable? Nah. Bad advice. But never be out of emotional control unless you're working through it with a therapist? That's good advice, that's what they get paid for. Losing emotional control with anybody else is unfair to them, not constructive, and unnecessary. It's 2023, let therapists do the therapy part.