Thank you for your question. I’ll try to answer it briefly and concisely. SJ-3, Zhong Zhu, Middle Island, indeed has an influence on the thyroid, which is located in the transitional area from Heaven to Earth. As you know, this area is partly regulated by the San Jiao. It is not without reason that the hormonal functions of the thyroid are influenced by the combination of the Yang Wei Mai and Dai Mai (the opening and supporting points are SJ-5 and GB-41).
It is not only van Buren who mentioned SJ-3 as having an influence on the thyroid; I have also encountered this in French acupuncture books (Dr. J. Lavier from France was the first acupuncture teacher of vB).
I recall several conversations with vB in which he told me that the thyroid, as an organ evolving from the embryonic stage to the adult organ, is connected with the Heart, and that the function of the thyroid is linked to the Spleen; this is also the position from which the functioning of the thyroid can be diagnosed. Apologies, my memory is a bit unclear, but he also mentioned (i think) that Liver Qi plays a role in thyroid function.
In my experience, SJ-3 is less effective for hormonal deviations of the thyroid but can be useful in the early dysregulation of the thyroid. SJ-3 resonates with the three Mu points of the San Jiao: CV-17, CV-12, and CV-7, as well as with CV-5 and, as you already mentioned, CV-2. In this sense, SJ-3 helps regulate the balance across the different Jiao of the body. I have never come across the idea that CV-2 is related to Jué Yin. I understand your reasoning, but as far as I know, it is primarily associated with the Liver (and Gallbladder).