Meta has a long history of breaking the law. I have no doubts Meta will have access to the personal details once you've "verified your age". They'll know WHO you are, as accurately as possible. Can you imagine how much that it worth to Meta, history's largest harvester of personal data? A whole lot more than $2B.
Now, based on their ruthless disregard for the law, do you think they're just going to use it to sell your ads?
They lobby for because then they can collect biometrics from kids and then reject them. So they don't serve underage kids , no fines but they do get data.
They will collect it from everyone to prove your age.
The question only that is it worth the gamble by Meta, as in how many people would rather leave the sites (from Whatsapp to Insta to Facebook) than give them their ID