It's only by sharing and discussing trauma with a friend that I was able to discuss it with any therapist/mental health professional

Therapists, mental health nurses, doctors aren't a replacement for a friendship. Why? Because a MH professional will not have the pre-built trust for you to safely ask them about things. A MH professional will not have the level of contact time to bring up those kinds of topics (which aren't things brought up within an hour, unless pre-practiced with a friend to make them something you talk about like clockwork). In a therapy context, someone could bring up years of abuse for the first time to anyone, and then the session would end and there would be no stabilisation or exploration of it.

The people who say don't talk to your friends about your personal problems and to talk to a therapist instead, miss that not everyone is comfortable talking to some stranger. For me, talking to a friend is what made it possible to be emotionally regulated enough talking about abuse with a stranger (MH professional). It made me know that these things are considered abuse or are considered bad by other people. It's what made me know that I could bring these things up and not be laughed at or dismissed. And that even if a MH professional wasn't on my side and considers me a mockery or invalid, at least one other person is on my side, so maybe it's just that the therapist/professional has a viewpoint that isn't agreed with by everyone else. Therapists do not ask questions, they do not make any effort to ask about abuse (but they are happy to have their GAD-7 and DHQ-9 questionnaires - those questions they're happy to ask, based on their own presumptions about what's relevant to ask about and what's not, which are based on their own normative life experiences).

A friend also gives genuine empathy and knows you as an overall person, rather than through only the lens of some pathology or problem. To be only seen through the lens of a problem is to be alienated from the full self. A friend can see your strengths and give genuine feedback and is a real person, a therapist is not trustworthy as an assessor of how real people will view you.

I go to MH professionals and they think it's a big deal I talk about huge amounts of abuse. It's not a big deal, because I'd already spoken to a friend about it.

The attempt to replace personal conversations with friends with therapy conversations is dangerous and will leave people stuck behind, because a professional relationship lacks qualities of a normal one (the most obvious being contact time and context of a longer duration of your life). They are simply not the same and therapy alone shouldn't be characterised as a full replacement for talking to friends, even in the very beginning stages (such as abuse disclosure or mental health issues disclosure).