It also mentions rolling over BNPL debt into credit card debt
This is like using one credit card to pay the bill from another.
Imagine for a second that was unrestricted. You could delay Credit card A's payment due this month indefinitely by paying it down to zero using Credit card B. Then, the following month after Credit card B's statement closes pay it down to zero using credit card A before card B's deadline.
You have in this case: 1. Not paid any interest, since you paid both balances down to zero within the grace period. And 2. Extended your deadline out 60 days by just one cycle. 3. Magnified the amount of debt you own.
Eventually you are going to find the money and pay it down, but most likely people who would do this would keep the game going as long as possible until they blow up. Card company A and B have no incentive to allow this, because you'll largely avoid interest payments at all, AND for all they know the final debt will be with card companies H, I, and J. There's a high chance debt will be defaulted, or at the very least they won't get interest or enough interest to offset their risk.