well actually

the older they get, the girls at least, the more circumspect they become, particularly around strangers, but in general also, i find. before puberty almost anything goes, and strangers are often the most worthwhile targets.

almost anything goes, before adult social routines kick in, and so many factors are involved...

spying is not substantially any different from acting out (as 'they' call it) in public - it's just rather more common to find out about sex in private, sex being what it is in society today - how many kids haven't seen things the adults probably don't know they've seen?

factor for personality and experience, older brothers and sisters, uncles whatever, think back to the kids you knew in k1 and 2, and you gotta grant ten percent at least are going to be working on working out what working it means... ten percent is a safe bet, i'm certain it's way more than that...

by nine or ten i was pulling stuff like that on certain teen/adult women myself, but having better luck with certain men, and i wasn't nearly as elegant about it as the seven y/o in question, and i knew full well i wasn't supposed to be doing it - plausible deniability is an adult explanation for an old game many kids learn to play very well.

unfortunately in uncle sam's bit of america, the adults are catching on - our intrepid reporter's encounter might well be in danger of capture and incarceration in a home, if she should happen to fetch the attention of thou shalt not advocates...

but nobody born with the parts isn't going to want to play with them, unless they've been severely traumatised. add an extrovert to the mix, someone smart or lucky enough to be able to pick positive experiences, or simply safe in the knowledge that she'd be rescued (by say an older sibling, in or out of cahoots) if she fucked up...

i'm just guessing at the why and how, i'm trying to describe the reality.

kids + bits = sex, it's elementary.