What is 'your experience of gender', I genuinely don't know what you mean by that.
I wasn't assigned a gender at birth. My sex was observed
Yes, your “sex” was observed. Well actually, (most likely) your genitals were, which provide a mostly accurate (but not perfect) “proxy” for what we think of as “sex”. Your gender was then assumed from this. But gender is so much more than genitals.
By way of one simple illustration of this, my 4 year old isn’t particularly interested in genitals, (I’m not sure how much she even knows about body parts beyond her own) , but gender is clearly very important to her. At the moment she is in a very “I’m a girl, so I only like playing with girls, girls are better than boys, I only want girls at my party, etc” phase, (despite my best efforts to dispel her arbitrary stereotypes and judgements of course). This is a perfectly normal and fairly universal state of childhood development. It’s part of gender identity development.
For people who aren’t trans, gender is so obvious it often goes entirely unnoticed .
Although not exactly comparable , we can look at other forms of majority/ minority difference to see a similar pattern. For example, it might not occur to a person who has only grown up surrounded by people with one type of way of speaking, that they have a localised accent. Not a perfect analogy, but perhaps you get the point.