Personally, for me it’s the idea that just because you don’t experience something (dysphoria, or being a gender other than what society expects of you) that doesn’t mean those experiences aren’t valid.
I get sooo tired of the response “I just don’t understand! I love being my AGAB! Why can’t you just get over it?”
That being trans is personal and that I don’t owe them an explanation for them to be supportive. I hate that most cis people only support us after we invest many hours of explaining what being trans is like. Why can’t they support us unconditionally?