The "prediction" of Figure 14 (B) (reproduced below in Figure 8(A)) is merely that a dashed or broken line tends to be perceived as a complete edge, which in turn tends to be perceived as a corner between two surfaces, especially when other perspective cues are consistent with that interpretation. This explains why Figure 8 (C) is seen as two rectangular surfaces in depth, rather than as a hexagon in the plane of the page, as seen in Figure 8 (B).

Figure 8.