cynical or sardonic?

I know that the people who write crossword clues are deliberately pushing boundaries and stretching the links between words that are in the same general area of meaning so as to create clues that don’t have an obvious solution.

However, every now and then I find myself mildly outraged by what I think is an erroneous connection. Today it was cynical  as a synonym for sardonic. I do not think that these words have the same meaning.  True you can talk about a cynical smile and a sardonic smile, but the first implies disbelief whereas the second conveys a sense of irony. Irony and disbelief are not the same.