You can be something and yet remain remarkably ignorant of many aspects of it, the history, the culture, etc. And someone who is not it may very well know aspects you don’t.
For example a young gay friend of mine was showing off the pink triangle design on his checkbook and was quite surprised at the history of the pink triangle going back to Nazi Germany and the Holocaust. He hadn’t a clue. He may know more about being a man and desiring other men than I ever will, but at at that point, there was much about history and even politics that I could teach him.
My gf thought the piss shiver she experienced was caused by the the alienation she felt to her body and her phobias related to bathrooms. While her experience of it is mediated by that, the piss shiver phenomena spans the sexes and is experienced by many not at odds with their body. Letting her in on the fact that cis women experience it too helped her feel better about it and a smidgen less at odds with her body.
We don’t generally expect experts in an area to experience it first hand. We accept that men can be gynecologists. We accept that women can be urologists. We accept that men can be experts in women’s fashion and hairstyles and yet not want to wear women’t clothing or hairstyles.
I can tell you that after living for a dozen years with a partner who is a trans woman and having done a great deal of research into various aspects, I have a good deal of knowledge about trans issues. I will never know first hand what being a trans woman is like, but I have knowledge that many trans women can benefit from, some of which was nontrivial to come by. One example that springs to mind is that I can tell you for certain that trans women on hormones may well be fertile long after that is expected to be the case. Another is that I know from personal experience that there is at least one home electrolysis kit that really works. Also, I know something about emotional swings related to hormonal changes.
And so I will continue to learn about trans issues, listening to trans women talk about their experiences, and I will also continue to offer information about trans issues as well as opinions and advice.