Completely agree it’s not for the child to carry the burden of acceptable hirsuteness for a female.
I had blonde body hair as a child. I wanted to shave as it made me feel a bit more grown up. My mum who only started shaving her body hair later in life said I didn’t need to and she wished she hadn’t bothered as she thought it grew back darker. She didn’t try and stop me though, just advice.
luckily I had a pretty good school education in that respect and they went through puberty and body hair issues, explaining shaving doesn’t change colour or thickness (it’s like cutting the hair on your head).
I shaved my legs and armpits, had teachers with full underarm hair and didn’t think much of it.
Today I sometimes shave, sometimes don’t. I epilate sometimes, but not really that bothered either way. I’ve noticed more people choose not to shave/wax/etc., or are just happy to display hairs between waxes.
People saying ‘I didn’t need to’ is a bit odd out of context, is it that they are not bothered by body hair in general, or they only think people should be bothered by body hair if it’s dark?