The debate belongs to a wider kalām dispute over reason, revelation, and divine acts. Some Muʿtazilī theologians argued that God must do what is aṣlaḥ—the most beneficial or appropriate—for His servants. Ashʿarī theologians disputed that alleged obligation.
The difference is methodological, not merely verbal. A claim that an act is rationally obligatory upon God needs an argument; denying such obligation does not, by itself, deny mercy, wisdom, or justice.
The famous three-brothers exchange tests this principle through a hypothetical scenario. It should be treated as a theological argument, not as a report of three real children whose individual destinies have been disclosed.