Possible sources of noise in their experiment could be ignoring word polysemy and data sparseness of word-feature cooccurrence in the corpus.
extending the rationale of Weeds et al., we suggest that if the meaning of a word v entails another word w then it is expected that all the typical contexts (features) of v will occur also with w. the characteristic contexts of v are expected to be included within all w's contexts (but not necessarily amongst the most characteristic ones for w).