Analingus has nothing to do with scat.
From a comment left on one of my other sites I discovered that some people assume that this form of ass worship is a form of coprophilia. With care on the Domme’s part there’s no reason for the submissive man’s tongue to encounter fecal matter.
Analingus can be an erotic practice as hygienic as any other.
Some people make wish to make it more intense with filthiness but that is not a requirement for the performance of analingus.