Because whatever happens in court (if it gets that far), they'll have years of appeals to go, and that'll be some future Google employee's problem not the current people.

Like when governments agencies ask to both "disable all tracking of what their employees do on the platform", to ensure private data and GDPR like stuff are ok. They also ask to specifically "enable full logging of all access to their data" for security reasons.

So: "sed -i 's/tracker/logger/g' codebase" and everyone is perfectly happy.

I wonder does GDPR specify different categories of consent which must be specifically and separately requested?

Though what you're describing would also be illegal. GDPR does not allow requesting consent for such broad data processing just to fulfill a legal requirement to verify the user's age, and then denying access to the service if the user understandably refuses to give consent.