Spelling errors also are sometimes not introduced by the author, but by the typesetter or publisher. In a preface to the Lord of the Rings, Tolkien complains about how many revisions it took to get typesetters to type the book correctly, especially with the words that he had made up or created new conventions for (elves vs. elfs, for example).
I suppose Tolkien’s work would be an exception, especially at the time. Typesetter seeing a made up word would correct it - and for most books it would have been the right choice.
