Ok, so if the reason you are off work is anx/dep/ins and they ask for a report about why you are off work it will detail your anx/dep/ins not your entire medical history. Just like they wouldn't mention your previous respiratory condition, and the report about your resp condition only discussed your resp condition.
(Usually the request for a report will be worded along the lines of "employee is off due to anx/dep/ins, please provide details of how this affects them in workplace, any adjustments, etc" , so it's already ringfenced.)
But if this scenario happens, all you have to do is speak to your GP. They sound like a reasonable person who has listened to you and respected your wishes in the past. There is no reason to think they wouldn't do so again.
If it sets your mind at rest, maybe write down somewhere safe what your plan is if they ask for a report. So "I will make an appointment to speak to my GP to discuss it" perhaps. "My consent is central to any report that is issued." "My GP has always respected my consent in the past." Maybe a note that you can call the Acas Helpline if you want employment advice on the process. Things like that.
It might help you feel more in control and able to take a break from actively worrying if you've got a plan written down safely for if you need it? (I do appreciate that this thread is already you doing that too.)
Victim is an objective descriptor. It's not a slur. It doesn't infer anything negative about you. It doesn't redefine you. The judgement you're placing on being seen as a victim is coming from within yourself not other people. Trauma makes us feel ashamed even when nobody else is actually shaming us. (And not all trauma is caused by humans, so people don't always make the assumption it was.)
At least, that's my view as someone else living with trauma and how I try to stop uninvited feelings of shame from crushing my soul.