I am not an expert on medical science but I will share my view based on the Chinese martial arts perspective - combative anatomy. It is personal understanding and by no means an advice to exercise accordingly.
First and foremost, muscle play an important role in work (energy producing) in western anatomy. What type of work a muscle group does or rather can produce depends on the composition of different muscle fibers that are presented (ie slow twitch, fast twitch A or B). So then you train accordingly with aerobic or anaerobic to get the desired result in the western sports model which does not necessarily view stretching as work or energy producing. Bones and tendons don't even matter that much.
Chinese model however sees things a bit differently based on Xue (blood - yin attribute) and Qi (enery - yang attribute). Xue Qi is the Liangyi (two archetypes) which is yin & yang that are comparable and compatible to the yin yang of the "universe" Heavan and earth (Tian Di). In human term, Yin Yang expressed as 2 attributes Jing (essence) and Shen (perceptual-preceptive faculty) commonly known as Jing Shen (the spirit) precept.
In pugilism, Shen expresses its intelligent attributes through the 4 limbs (eyes, ears, arms, and legs); while, Jing manifests its brilliant attributes through the 4 extremities (bone-teeth, tendon-nails, boold-hair, and muscles-tongue). This is the Bagua (8 trigrams) of pugilism. In other words, pugilism is to "honor" the Heaven and Earth through exercising the Jing Shen. So you see why Jing Shen has a place in the Ba Fa (8 protocols or methods) of Pugilism. We can not exercise the bone or boold per se. But we can exercise on tendon (jin) and muscles (ji). However, ji is also relatively softer and on the service which by the way is considered similar in nature to skin processing yin attribute. This in Chinese view is not where "true" strength or power came from. It is the deeper layer and the relatively harder yang attribute, which the tendon has, that provides that "true" strength. The most crucial tendons, which are elastic sometime membrane like substances (collagen?) that have the property not unlike rubber band, are in the lower limbs. This is where "energy" is stored or rather resided. Surely when stretched and trained properly, they "yield" (pun intended) the most work or energy producing. No wonder in most "traditional" styles, strecthing the lower limbs is regarded as the priority. Strong kicks comes from strong tendon and it's an expression of the yang attribute. It is in this work that we see Kung Fu in its most fundamental form.
So Kung Fu is holistic and organic. It is a unification of mind, body and spirit as discussed above.