Complete correspondence between the arrangement of the Partzuf and the human form.
A Partzuf's arrangement exactly corresponds to the human form — limbs, organs, anatomical relations, all of it.
Op. 71 makes the complete-correspondence claim explicit. Whatever you see in the human anatomy — head, body, legs, organs, limbs, the relations between them — has its cosmic counterpart in the Partzuf's anatomical architecture. The chapter is brief but architecturally definitive.
The sod hatemunah principle from Op. 13 returns here in its strongest form. The human form is the cosmic template; every prophetic-anatomical claim about a Partzuf's structure is read by analogy to the corresponding feature of the human body. The 613 parts of a Partzuf (Op. 70) correspond part-by-part to the 613 commandments-and-limbs in the human-anatomical-and-ethical scheme.
The Sefirah is the simple light; the differentiation into particulars belongs to the Partzuf. This sharpens the Op. 17 distinction. Sefirah is the underlying simple-light power, undifferentiated. Partzuf is the differentiation of that power into 613 anatomical-operational parts. Klach's vocabulary settles here: from Op. 71 onward, Sefirah names the underlying power; Partzuf names the operational anatomy.
Op. 95 (A"A's Skull-and-Brain anatomy from Idra Rabba; Three Heads from Idra Zuta) is the operational deployment of the complete-correspondence doctrine for the most-treated Partzuf. Op. 101 (every Partzuf's Head requires Keter and Mochin) generalises the anatomy across Partzufim.