Google puts together a probable age based on the profile they collect about you. They 100% know they are advertising to some children, even if just by mistaken

Google puts together a probable age based on the profile they collect about you. They 100% know they are advertising to some children, even if just by mistakenly mislabeling children as older in rare cases. That's impossible to prevent through probabilistic means, so by implementing such systems they have accepted such an outcome.