That’s how I understand it. Cash is legal tender and has to be accepted to clear debts, so restaurants where you pay after you eat might not be able to refuse cash (though I don’t think there’s a requirement to provide change), though they can refuse all future business with you.
Cash is required to be accepted to clear a debt.
Cash is not required to be accepted to make a purchase.
That’s how I understand it. Cash is legal tender and has to be accepted to clear debts, so restaurants where you pay after you eat might not be able to refuse cash (though I don’t think there’s a requirement to provide change), though they can refuse all future business with you.