The 3 Internal Harmonies

Chen Zhenglei, details the 3 internal harmonies as Shen (mind) with Yi (intent), Qi with Li (strength) and tendons with bones ("Chen Style Taijiqian, Sword & Broadsword" pg. 96). This differs from other versions but the fact that he is a scholar as well lineage bearer make me believe that this is more than just an idiosyncratic interpretation.
Missing is the harmony of qi and yi. However it is often said that "Qi follows Yi" automatically. The addition of tendons and bones is interesting to me because of what I know of Magui style Bagua. Tendons & Bones are extensions of the Liver & Kidney networks, the two deepest in the body. Magui bagua's approach is to train Qi & Blood primarily. This is required to build up the tendons (and, I think, bones). To train more externally, working say the muscles, might appear to be quicker, but the gains are temporary and increases the risks of injury. Staying focused on training Qi & blood builds the body from the inside out.
Chen Zhenglei's inclusion of the tendons & bones, I think reflects similar thinking. The structure (bones and tendons) need to be harmonized, not forced or worked. This allows the proper opening of the body and the full circulation of Qi throughout all of the channels and networks. This pair is also provides a linkage to the 3 external harmonies (which describe the requirements of proper posture & alignment), making the 6 harmonies more integrated.