On what grounds do you claim that Aristotle misunderstood the Pythagorean–Platonic Metaphysics?
This is neither a personal judgement nor a provocation. The same observation had already been made in antiquity by those who had understood Plato without the mediation of Aristotle, drawing from the very same source from which Plato himself had drawn.
Plato does not elaborate an “original” philosophy in the modern sense of the term; rather, he studies and translates the ancient Wisdom transmitted through initiation, via various circles, among which the Pythagorean.
Aristotle, by contrast, was not an initiate and had no direct or privileged relationship with Plato. He merely interprets — and often criticises — what he is able to grasp: both the contents expressed in the Dialogues, and those conveyed through conversations with members of the inner circle of the Academy, such as Speusippus.
Every consciousness that has not been initiated, instructed, or re-educated in the contents of Wisdom tends, by its very nature, to translate into psychological and empirical terms principles that are, in truth, purely logical-metaphysical. Whoever aspires to comprehend the ancient Wisdom and Plato’s Idealism must first reconfigure the structure of the mind itself, passing from the “Logic of the Part” to the “Logic of the Whole”, with the aid of the archetypal diagram. Aristotle’s misunderstanding is therefore the natural limitation of a mind still bound to the domain of experience. The later Academics and Peripatetics — deprived of access to the original source — were unable to grasp Plato’s intention. Thus they transmitted to us an “aristotelianised” Plato, and therefore a distorted one, sincerely believing they were preserving the authentic version.
For a long time it was believed that Aristotle had been Plato’s "favoured disciple", yet it is more probable that within the circle of the Academy he remained an 'acusmaticos'. It should be remembered that no ancient source allows us to determine with certainty what kind of relationship truly existed between Plato and Aristotle.
The earliest testimonies portraying Aristotle as Plato’s “beloved pupil” are of later date and lack direct corroboration. There is no reason to suppose that Plato regarded Aristotle as the continuator of his own philosophy. The two in fact pursue profoundly different aims: Plato investigates transcendent Forms, while Aristotle studies Phenomena.
Neither Speusippus nor Xenocrates — Plato’s immediate successors as heads of the Academy — left us any direct testimony concerning Aristotle. What we know of their relationship derives from later sources, such as Aristoxenus of Tarentum, a defector from the Academy and later a disciple of Aristotle, who alludes to both personal and intellectual tensions between Aristotle and the Platonic Academy.
Later on, Cicero and Plutarch would retrospectively interpret this relationship as that of a master and his brilliant yet unfaithful pupil. The Byzantine Suda perpetuated the same tradition, depicting Aristotle as the gifted student of the Academy who “corrects” his master.
The figure of Aristotle as Plato’s “favoured pupil” is thus a later construction, born of the genealogical needs of historiography rather than of direct evidence. Hellenistic and late-antique commentators — and subsequently modern historiography — idealised that connection in order to trace a line of continuity between two systems which, in reality, stand at opposite poles.