The verification process using the German eID is. It is cryptologic secured, no middle man and the site owner only gets the information, if the age limit is fulfilled. Just because you can not imagine it means not that it does not exist.
And no, you don’t can trust the government on such things. That is why the software stack is open source and the functionality can be verified by the citizens. The CCC was involved to verify this …
By what means? Install Spyware on the kids device? Spyware that may have vulnerabilities and can lead to even greater risks of the kids? Smart idea …