A friend said he wants to take advantage of his child not being 20 yet to get them a credit card.

Then spend a few thousand yuan, intentionally not repay it, and let the card go into default.
Now credit reports are basically blacklisted for over half a year.
Then the credit recovery period is five years, meaning it'll be before age 25.
The purpose is to ensure that whether the child is in college or just graduated, even if they go astray or get led down the wrong path,
because their credit is blacklisted, they won't be able to get online loans or max out credit cards, thus avoiding early debt.
By age 25, they'll have some self-control and judgment, their credit will be restored, and nothing will be affected later.
This thinking is indeed top-tier.