I looked for that particular handout, and couldn’t seem to find it, but as a general answer, I would say it is tricky because jing, qi and shen can be either yin, yang, or yuan. The polarization mostly takes place in later heaven (hou tian), and the farther you go into early heaven (xian tian), the hundun and wuji, the more neutral it gets.
Pure neutral force holds the potential to polarize, so it contains potential yin and yang in balance.
From a vibrational perspective though, it makes sense – jing is slow, shen is fast and qi is the balancing point, or neutral center if we look at jing and shen as the two extremes.