Most of the debate about age assurance in games is about which method to use. Face scans, IDs, parental consent. I think the more important question is what each one should let a user do.
Some methods that I've seen used and work: A birthday typed in at signup gets you locked-down defaults and not much else. An age estimate can open up text and voice chat with people your own age. Anything that lets an adult reach a minor privately should need a verified account or a parents sign-off. Friction goes where the risk is, and most users never feel it. (Obviously context and platform matter TREMENDOUSLY)
None of these methods is perfect, and the mistakes aren't equal. Put an adult in a teen group and they get annoyed, and some borrow a younger relatives account. Put a 15-year-old in an adult group and every protection built for them is gone. Optimizing for 13, 16 and 18 becomes one of the most important points.
Most age checks happen once, at sign-up or when a feature unlocks, but accounts don't stay with one person. They get shared, sold, or passed down to a younger sibling, and months later the person playing no longer matches the age on file.
Banning every account that looks off would hit a lot of legitimate users, and doing nothing leaves the gap open - these are off the table for most programs anyway. We can do way better. The better move is to put the account back on safer defaults right away and ask for a stronger check. The kid stays protected while it gets sorted out.
Someone also has to own these lines. Where the thresholds sit, and what evidence each one needs, affects product, safety, legal and privacy all at once. If nobody owns it, each team nudges it toward its own goals and nobody notices the drift. It deserves the same sign-off process as a policy change.
And completion rate is a weak metric on its own. Id rather know how many accounts in teen groups turn out to be adults, how many kids end up in adult groups, and how long it takes to catch an account thats changed hands.