This is probably to be explained by the size of the lexicon as only ∼2% of the words in the whole 500ktoken corpus are not covered by the lexicon and the fact that including suffix features already deals with tokens not covered by the lexicon.
given that in the next section we perform experiments in which we drastically decrease the size of the lexicon used, we decided to keep for the the remainder of the experiments the more complex feature of MSD hypotheses given the longest suffix.