Right! Only XYLH develops and employs 'tendon power'.
I think not.
The intrinsic energy potential and core power potential of every true Internal Art, IMO, is expressed in every movement and technique as an elastic and flexible strength which emanates from the joints and tendons of the body. It generates a 'coiled spring' kind of strength which is often traditionally compared to that of an archery bowstring. As such, when the joints and tendons are properly stretched, while the limbs remain relaxed, and curved like an archer's bow, a recoil power is developed that can repel whatever it comes into contact with.
In application, the attacker's experience is much like sprinting at a fast speed in the darkness of night and then suddenly running into a clothesline or a thick wire securely stretched between two posts, or like a quickly rolling marble suddenly spun off to the side when contacting the rotation of a rapidly spinning top. This should be considered the norm in these arts, not the exception found only in one style or method.
Doc