I doubt it's presented as the final fact. It's probably more presented as an opening idea - something that kids can digest.
Like talking to kids about gravity and using the phrase "what comes up, must come down."
Nothing wrong with that when getting started on introducing a very complex subject.
You want grade school teachers to present undergrad biology courses to kindergarten kids? "Gather 'round, children. Take your pencils out of your nose while we look into phylogenetic classification this morning."