Posture #10 is basically fan through back. If you have ever seen Bruce perform Tai Chi as meditation and heard him talk about what is happening in this Tai Chi posture, you’ll understand what is supposed to happen in Bagua and in particular posture #10.
This may be the bridge to shen. It is still a Chi phase component, but the expansion of the mind that you are going for is at the end of the Chi phase. I think this is working primarily in the 3rd ventricle and the glands that are there but there is something else that may be more important to understand: linking to the body.
What dawned on me is how everything is linking to the body, organs, CSF, and the breath. Posture #9 completed an important circle in the diaphragm. I don’t think Bruce mentioned it, but IMO, that is what #9 was about. Here the movement of the organs is complete. They are coordinated with the breath (not really talking about breathing as much as the movement of the diaphragm). They are controlled by the CSF and they are linked to the pressures in the 3rd ventricle. The Taoist are keeping you grounded in your body. Everything is being linked to the physiology very purposefully.