Put your tinfoil caps on. I personally think Google knows this fact but has monetary reasons to not disclose it. If the advertising industry expected to pay say, 4 times as much when they advertise to children, Google would be all over that.

Also, whatever your CTR is, it becomes a lot less meaningful if it turns out the majority of your users are illiterate and between the ages of 1 and 4.

I guess the money making scheme/scam here would be an advertising firm where you make commercials that incentivize viewers to put their finger on the video during the ad and appeal to toddlers.

An ad like "Put your finger on my face! Owww!" may deliver obscene "convergence" numbers. So long as the clients don't figure out the demographic of their viewers, you get the big bucks.

Probably on their parent's account.