In Mann’s description of Manaka’s Shokanten points, those are points that become tender when the corresponding division is affected and can therefore be used both diagnostically and therapeutically. KI16 is specifically given for Lesser Yin — Heart/Kidney. So there is certainly a basis for considering KI16 when Shao Yin itself is involved, but I would not choose KI16 simply because Shao Yin is weak on the pulse. The first question would be why Shao Yin is weak and what kind of support the division needs.
Another indication for using the Shokanten points comes from the Nine Continents pulse diagnosis, where the pulse is assessed in different areas of the body. A weakness of the pulse in the corresponding area can provide an additional indication for using the relevant Shokanten point.
In your example, for an HT Branch person, Shao Yin is important because the Tu Tien energy of Shao Yin is needed for the HT Branch, and the authority and quality of the vertical axis are important here. So treating Shao Yin seems reasonable. The next question would be what kind of support is actually needed. Is it necessary to strengthen HT, or both KI and HT? Is there a need for more Yin, Qi or Yang? Or is there a deeper issue within the division and its connection with the constitutional root?
This last situation would point more towards considering KI16 as a Shokanten point. As we were taught in the courses, Shokanten points can be considered when there is a more prolonged and deeper issue connected with the division, often involving both physical and psychological aspects, and when this is also reflected in the pulse. They seem to regulate the division at a rather basic level.
The direction of needling is also important. Needling KI16 outward towards ST25 makes a connection from prenatal towards postnatal, while needling towards REN8 brings more nutrition towards the constitution/prenatal. So perhaps KI16 should not be seen simply as “Shao Yin is weak, therefore use KI16.” It would depend on what needs to be done with Shao Yin and at what level.
Regarding the concern about bringing a pathogen further inside, I would be cautious about making this a general rule. The material we have does not seem to say that Shokanten points themselves necessarily bring a pathogen inward. It seems more important to have a clear diagnosis of the division and a clear intention regarding the direction and level of the treatment.