Most lexicographers are good spellers, if only owing to lots of practice. Lexicographers take the same view of language as other linguists. They know that language use varies widely in space and time and they spend much of their time charting its changes through history. They are therefore not shocked or surprised to encounter variation in spelling. At the same time, they recognize that there is a standard set of conventional spelling rules to which we all mostly conform and which assist good communication.
Everyone makes mistakes and lexicographers are no exception. Even now when most dictionaries are produced by large teams, errors ranging from typos to incorrect definitions can make their way in. After all, dictionaries are big books that take a lot of work to write.