لِأَنَّ التَّشْبِيهَ قَضَاءٌ لِحَقِّ الْمُبَالَغَةِ
Completing the resemblance is a way of fulfilling the demands of rhetorical intensification.
Calling a person a “sun” or “moon” does not assert that they have literally become a celestial body. It powerfully attributes a salient trait until the distance ordinarily perceived in comparison seems to disappear.
Two levels must be kept separate: external fact, where the human and sun remain distinct; and rhetorical assertion, where likeness in beauty or brilliance supports their imaginative identification. Hyperbole operates at the second level and does not overturn the first.