«أَوْ لِتَكْمُلَ لَذَّةُ الْعِلْمِ بِهِ»
Or so that the pleasure of learning the matter may become complete.
Knowledge received after anticipation can feel more satisfying than information supplied without expectation. A general indication creates the wish to know; the subsequent specification fulfills it. The delay is justified by this additional cognitive effect.
The principle does not warrant making every statement into a riddle. Whether immediate clarity or brief expectation followed by disclosure is better depends on the audience and the communicative situation.