This paper gives a structural explanation of axial grade blindness in torsionful twistor transport. Using the (U(1)) charge decomposition of the reduced spinor slots, it shows why axial torsion can appear in transport and surface obstruction data while disappearing from the curvature-grade readout. The result recasts the computational altitude separation of T17--T18 as a selection-rule statement.
Hiroyuki Shioiri (Sat,) studied this question.