Figure 6 shows that model M=B1+B2+B3 does not fit well, as SRTE dataset exhibits a rather different distribution from both BRTE datasets.
it is clear that had a model been fitted on SRTE data, the coin flipping probabilities for the clear types, B1 and B3, would have to be moved towards 0.5; that is, an average annotator in SRTE dataset had worse ability to detect clear 0s and clear 1s than an average BRTE annotator.