I don’t think witnessing it is really enough to understand it for everyone.
For example, I don’t fit in with traditional gender norms. Yet at the same time I don’t feel like I was born into the wrong sex/gender. And if I was born as the opposite sex, I think I’d be pretty indifferent about it. I don’t really care either way for myself, personally.
I have both transgender and nonbinary friends and I simply don’t relate to their struggles. While I don’t feel like I fit in, I don’t feel like I’m the “wrong” gender/sex either.
I respect transgender and nonbinary individuals. And I think they absolutely deserve to live their life the way that makes them the most comfortable being themselves. But unfortunately, even witnessing this stuff fist hand doesn’t mean I’ll ever personally be able to understand gender dysphoria.
I’m supportive, but I’ll never truly understand. But I don’t think you have to fully be able to understand to be an ally.