rednsparkley My 11-year-old is doing the same as your 12-year-old, though my DD added in microbangs once it got long enough to be in her eyes. Like you, I'd no control over my hair as a child so it's been... interesting if cringey at times watching her figure out her hair.
My hair is going to be 'messy' unless I follow my daughter's example in shaving it. I've been tempted, it gets frizzy so easily, but when it's smooth-wavy, the temptation fades cause it just feels like me.
Kinda laughing at needing a genuine reason to have long hair - wtf is a genuine reason for long hair? Sure, for some middle class parents it's a badge of honour to let their young sons have long hair - I've seen it associated with not confoming to British gender roles which I guess can be seen as a middle class thing in the UK - but I live in a mixed class area where several of my teenage daughter's friends discuss how their parents won't let them cut their hair (this comes up a lot as my daughters both started secondary with short hair). Girls whose hair is apparently their family's pride and joy & just looks too nice to cut. Class cultures is weird and localized like that and I think it's weird for parents to do whichever sex the child is, but no one needs a reason for long or short hair.
Idly wondering if the 'give them choices' argument extends to choices with which their parents do not concur
For some parents, it probably doesn't - I've definitely seen some loud proponents of choice be the ones who swoop in about how they'll decide what's best. Others, we come up with compromises or choices within contexts & limits or just deal with choices we don't like. I certainly did not choose to live with a child with a mullet over the first lockdown because shaving just the front of the head seemed like a great idea somehow (so happy when they grew out). I do have a limit that I don't buy hair dye - having been forcibly bleached as a child, helping my son the first time he wanted to add semi-perm. to his fringe was already a painful stretch, but it was his own purchase and he doesn't attend anywhere that cares if his hair has a magenta fringe so it was his choice.
I remember in infants school during stories our teachers let us plait each other's hair while we were listening. Like a load of monkeys grooming each other. grin. It was so relaxing having someone play with your hair.
I did that so much in school! There was a thing then at my school about trying to do as many tiny braids as possible, and we do them while the teacher read, it was very nice. I still like having my hair played with.