Assuming the opt-in was legitimate and the bank actually has an overdraft payment program that authorizes ATM and POS transactions against a padded balance, I don't see that there's unfair treatment if the pays and charges for one customer's POS OD (opted in) and pays and doesn't charge for another customer's POS OD (no opt-in, but had to be paid).
If a bank solicits opt-ins under false pretenses when it actually doesn't have an automated overdraft payment program for ATM and debit card transactions, I'd call that a UDAAP violation, and Randy has suggested as much in earlier comments on that question. Candidly, I'd welcome an FIL from the FDIC to put that practice to bed in black and white.
John S. Burnett
Fighting for Compliance since 1976
Bankers' Threads User #8