Has anyone looked into this argument?

Not at all. 

He did in the notes say that it was different than Aquinas's argument though, although I think you are probably correct. Perhaps he felt it was an add on though, which I think this does support:

" St. Thomas in the Summa states the henological argument in a somewhat different form. We find, he says, that in the world of experience some things possess more, some less of goodness, truth, unity and being. But we cannot speak of more or less of any perfection unless that perfection is, somewhere or other, realized in its fullness: and as thus completely realized it must be the cause of all its inferior exemplifications. It follows that being exists in absolute perfection, and as the cause of all finite things. The assertion here made that being is found in a diversity of grades is established from the correspondence of being with the attributes of goodness, unity, etc. The measure in which a substance possesses these attributes is the measure of its being. Unity will serve as an illustration. Substances, it is evident, exhibit this attribute in very different degrees. An organized animal is more perfectly one than a plant, which can often be multiplied by mere division: and a plant is a truer unit than a fragment of some inanimate substance. Man, on the other hand, in virtue of his self-consciousness, is more perfectly one than any of the lower animals. A pure spirit is a more perfect unity than man. The more fully a thing is a unit, existing in and for itself, the greater is the degree in which it possesses substantial being. Only the individual substance is properly said to be (infra): and our argument shews that this substantial being is realized in many different grades. Moreover, these grades demand the existence of a highest grade in which the perfection is fully realized. Were there not such a supreme realization the terms more or less would be meaningless The various manifestations can only be grouped together as possessing a common nature, if there is an ultimate norm to which the several individuals approach more or less closely. This may be exemplified in the case of a circle. We should have no right to group circles together in a class and call them by a common name, did not the circles which we draw, approach, however imperfectly, to an ideal type, which the mind can apprehend, though concrete matter does not admit of its perfect realization. What has been said in the text will shew why the argument enables us to conclude to the real existence of the supreme degree of being, goodness, etc., though only to the ideal existence of those inferior perfections, which demand material embodiment. The argument was derived by the Schoolmen from St. Augustine. He thus establishes the existence of God in De Civ. Dei viii c.6. P.L. 41, col. 231. Cf. De Div. Qq., lxxxiii., q. 45; De Doct. Christ., c. 38; De Trin. V., c. 10, n. 11. The proof in this form is generally called the argument from the degrees of being."