«كعنقود ملاحية» presents the Pleiades through the image of a cluster. It is not merely an assertion that white points exist: the salient feature is the grouping of several bright units in a recognisable arrangement.
Analysis:
Subject: the apparent grouping of the Pleiades.
Comparison image: a clustered bunch of small units.
Point: the overall pattern formed by brightness, proximity and arrangement.
Describing the light of just one star would not capture the full point. The analogy depends on a relational pattern among the elements, making the resemblance composite rather than a list of independent brightness comparisons.