Some people live to very strict rules about what boys , girls, women and men can look behave / like / do / say / eat / do for jobs & hobbies . I know this is their religion / ideology / belief system and they are of course entitled to believe in it.
Personally I don’t agree and I’ve raised my kids to know that they can have any kind of clothes / hair style / hobby / interests / personality / appearance they like, regardless of their sex. They don’t need to live their lives in tiny boxes created by others, they can just be themselves, they are perfect the way they are.
I also hate the homophobia implied in the “ you can’t dress your son in a pink tee shirt as it will turn him gay “ nonsense . Your child will be straight / gay / lesbian / bi as an adult whatever you dress them in and that’s ok too.
If I saw a small child holding a frog / jumping in puddles Id talk to them about what they were doing . If you feel the need to know if the child is a boy or girl to interact with them, it’s you who has the problem.
If the parent has a concern that you might misgender their children , they will nearly aways signal by saying “ Yes Sophie loves frogs, she has three frog toys on her bed “ or “ Isaac wants to be a scientist when he grows up “.