6 conformations – Yin phase (Closing of a door). Yin sinks away its predominant movement closing and down, so jue yin closes but don’t we need Tai Yin as the mechanism that ensures that the door doesn’t completely close and not a continuation of closing as indicated. ie jue yin as the controlling mechanism?
Your confusion derives from your attempt to apply some of the qualities of yin and yang in the wrong context. SuWen6 is talking about the way Yin and Yang generate cycles. A cycle implies a perpetual return and can be better represented by the metaphor of the movement of a door. Jue Yin ensures that the door opens again into the yang just like winter opens into the spring (the return of the yang) instead of closing into an indefinite storage or the night opens into the day.