Not all QMessageBoxes follow Apple's Human Interface Guidelines for "Alerts"

[crwood]

Some instances of QMessageBox are still using the setTitle() method, which is ignored on macOS, thereby resulting in a loss of potentially important information to some users. Accordingly, all instances of QMessageBox should be updated to conditionally use the setText() and setInformativeText() methods if the underlying platform is macOS/darwin (and use setWindowTitle() and setText() on other platforms).

See also: https://developer.apple.com/design/human-interface-guidelines/macos/windows-and-views/alerts/