hi roland
bruce has said that in taiji generally you keep the tailbone dropped, although there are some styles where you tuck it.
he’s explained it in taiji as dropping the tailbone through the legs.
bagua for sure has more of a tuck, which gets the “fuck the foot” feeling going on.
in the big picture, though, since most of us have some rearward tilt to our tailbone, this question is a matter of degrees, since if your tailbone is tilted, you gonna have to rotate it somewhat to get into the dropped position.
in any case the main goal is that are trying to integrate the movement of the legs and the movement of the pelvis and spine. and get the energy smoothly flowing through the legs.
the place where I really felt this connection was when I learned bend the bow chi gung, although i felt it to an extent with the bagua walk. a lot of that may have to do with timing, though, cause I learned the BTB years after I started practicing the bagua 4 step walk, it probably helped “set the stage”.
hope this helps…