My DD was a failing to thrive baby. Sh had virtually no social interaction until the age of two, apart from her older brother and some male cousins.
As a result she had a number of physical and developmental lags, and, when she eventually got there, found other children at nursery/playgroup very confusing.
No gendered toys, not gendered clothes - there was not enough energy to play, nor to dress her in anything but grubby hand me down babygrows. (Elasticated waists were ruled out because of her illness.) At the age of two she announced she was a boy. My guess is that her brother was a boy, and her role model.
She kept this up till the age of 8/9. I think the grandparents found it slightly confusing, but we just let her be. Teachers, and other parents and children were accepting, and she went to boys parties and playing in the school football team. Most mums said they were happy that their sons were friends with a girl, bar one who was almost the exception who proved the role who clearly thought I was failing as a parent by not forcing my DD into a gender stereotype.
By 9, the other girls had stopped wearing pink and had changed into jeans, and my daughter found her group of straight-forward, academic, sporty, girls. I don't know if it is a s a result of her early socialisation but DD is very comfortable in mixed friendship groups and has maintained good friendships with both boys and girls.
My concern is that all of this would be much harder today. Rather than let me just parent according to my instincts, well-meaning people would leap in and press me to seek some sort of "diagnosis". It feels as if awareness of gender in young children is heightened, and that gender non-conformity is not simply a child being quirky, as small children are, but some sort of physical thing. A boy brain or something, caused perhaps by too many hormones during pregnancy or similar cod-science.
My daughter was fine as she was, being who she was. The all important thing, especially given her difficult start, was that she was thriving. I think today, both she and I would be much more anxious, as we would have to deal a society judgement on her gender-non conformity. I feel for parents today.