Stumbled over the new offset parameter of createMatches:

This tells me that something hasn't been understood because FuzzyScore itself already has the notion of an offset. The idea is that no substrings are created but fuzzyScore (and its cousins) should be called with a wordPos which is the offset at which matching should start inside a word. That offset is that captured inside the score and used when creating matches. The new offset doesn't fit into this.