Sensory (ḥissī) means accessible through an external sense, not merely through sight. Hearing, smell, taste, and touch also qualify. Thus redness of a face, softness of a sound, fragrance of perfume, and smoothness of silk may all be sensory features.
إما حسيان كالخد والورد
Or both terms are sensory, like a cheek and a rose.
Their shared colour or delicacy can be perceived visually, so the pairing exemplifies sensory-to-sensory simile. Yet two things perceived through another external sense are sensory in exactly the relevant technical respect.