Preposing is not always about strict exclusivity. It may foreground a description to create admiration, anticipation, or thematic prominence. Poetry often names a remarkable quality before developing who possesses it and how far it extends.
«له همم لا منتهى لكبارها وهمته الصغرى أجل من الدهر»
He possesses ambitions whose greatest have no limit, while even his least ambition surpasses time.
Beginning with «له» links the coming description to its possessor and creates expectation. The subsequent statement about lofty ambitions develops the initial impression of greatness.
The function of preposing must therefore be discovered from context: restriction in one sentence, praise or anticipation in another.