"talking about your mental health" does not mean re-parroting your trauma. there's understanding, re-framing, forgiving, all kind of other things that go beyond the limited belief that talking just calcifies trauma.
Yes, me. I suffered some serious depression that I cured through therapy and medication. Discussing it openly with my family and friends certainly helped.
As the saying goes, recognizing that you have a problem is the first step to being able to solve it.
venting is a form of talking about mental health. there are other forms that the problem statement doesn't apply to, like your examples. but the statement does apply to my example, therefore we can't say that talking about mental health is exclusively a positive behaviour.
Can you think of anything you can do that is exclusively a positive behavior? Drinking water in excess kills you, excess breathing kills you, excess exercise kills you, I think the logic here can be used to sow the seeds of uncertainty in nearly anything, honestly.