Cross Domain Thinking is a natural abstraction from the notion that there is utility, fulfillment and value to be found in mastery of a multitude of skills. What one truly learns as they pursue this is that few concepts are domain specific.
Once you learn how to learn the applications of this skill are limitless. The examples cited in the original post are rooted in an overarching concept. It boils down to the fact that one is able to truly innovate and produce value if:
a) They grasp multiple domains of knowledge
b) They learn to generalize domain specific ideas and apply those concepts to other areas of their knowledge
That is the definition of Cross Domain Thinking.