What I mean is that for customers, secured credit cards and debit cards have roughly the same risk, but banks have obligations to offer checking accounts fairly but offering the equivalent credit-building account is up to their own discretion. It’s considered lending even though they’re lending the customer their own money.

Do you feel that the "discretion" violates the equal credit opportunity act? Technically, credit discrimination is illegal, but I could see a bank taking liberties with people who don't have the means to protect themselves.

Given that the risks to “creditors” (banks lending money back to people who own that money) are equal for debit and secured credit cards, and that the risks to “debtors” (people who would be using their checking account to build a neutral-at-worst credit history)…

Having the means to protect yourself is the baseline definition of a secured credit card. That’s why it’s secured. You’re starting with some positive balance and spending your own money. That’s what debit cards are too. The liberty banks take is choosing who gets to benefit from their normal spending of their own money being considered as credit at all.

Well they work like debit cards in a way, you can't overdraft and you build credit with it. It's what's recommended for newcomers to the US. But I'm not sure they're really the same given that your credit limit will be as high as the spare amount of money you can keep as security in your bank.