If a child wants to be "protected" online then it would be up to them to enter their actual age. But you are right, the government will take any excuse to get users verifying their age.
> "We want social media companies to confirm they will not implement end-to-end encryption until they have the technology in place to ensure children will not be put at greater risk as a result."
Most of these companies already know the users birthday, if this is only about child abuse then instead of adding backdoors for everyone, why not just disable end to end encryption conversations for users under 16?