Why are adults expected to desexualize kids?

One common ToS violation across a variety of online spaces is the supposed act of 'sexualizing minors', as if nobody below the age of 18 ever has sexual feelings or could possibly be the subject of sexual desire. It should go without saying that virtually nobody would actually believe such an absurdity if they really thought about it, and that the insanely broad brush has been procured to protect companies against legal and social censure. But I do think there are a lot of people who believe preteens are entirely asexual. They could hardly be more wrong.
This past weekend, it was a constant battle to stop my new YFs being 'inappropriate'. They are all preteens, with little kid voices, clearly not having started puberty. Yet they repeatedly did things like grabbing each other's dicks, trying to grab mine, even play-humping each other with clothes on. And I did tell them not to, many times..
Now I don't pretend that preteens possess the same feelings of lust that adults are accustomed to. I don't imagine they go home endlessly fantasizing about giving their friend a BJ, needing to rub one out as a release. Such is a testosterone-fueled state of affairs, starting in adolescence.
But absent of pure lust, sexuality can still very much exist, just in a different form. For children, it's more a matter of curiosity, of fun and games, and of pushing at the boundaries imposed on them by adults. These are traits they possess in abundance. Not being allowed to do anything sexual at my place, my most playful YF kept feeling my facial hair, grabbing my ears, even lifting up my shirt sleeve and pulling at my armpit hair. Perhaps consider it a need for visceral connection in whatever form?
Adults who have lost touch with their inner child will scream that what I'm describing is not really about sexuality at all, reducing it to nothing more than pure silliness. And while children absolutely do sexual things as pranks, and as a form of rebellion, many of their expressions remain very much an immature form of sexuality. If you disagree with this characterization, consider what you'd be charged with if you didn't say no to them playing some of these 'childish games' with you as an adult.
Unfortunately, despite being a BL, I feel the need to discourage any sexual games with such presumably being the expectation of parents. I like living where I do now, and being a teacher, and I enjoy spending time with my cute and cuddly YFs. Is it not fundamentally wrong, however, that we are forced to shut down normal childhood sexuality as if it were some grave sin? It feels like desexualization by force, caging children's natural curiosity and playfulness, all because we feel that other adults demand it.
Of course, it would be remiss not to mention that there are indeed situations where adults do impose adult sexuality on kids. I doubt your average 10 year old would want to be, for lack of a gentler way to say it, fucked in the ass. But to conflate this with children lacking anything resembling sexuality, and to suggest that all expressions must be equally unnatural and imposed, is absolutely insane... black-and-white beyond any semblance of logic.
And after writing this article, I'm feeling a bit guilty about being so strict.
As for the predictable retort...
Antis will no doubt scream that children generally want to do dangerous things and should be stopped. "You wouldn't let children play with explosives!", they might shout. However, explosives have a clear mechanism of harm, whereas sex play simply does not.
Yes, there have been studies 'proving' harm, sullied by sample bias, researcher bias, and secondary harm in prudish hellscapes like America. Still, I've seen nothing truly convincing, a piece that accounts for variables like whether the sexual contact was wanted, initiated by the child, or an example of immature sexuality rather than an adult imposition.
The "let kids be kids" people are among the biggest fucking hypocrites in the world.