In a way he’s like Weird Al - technically Al is a parody artist but he had an excellent mastery of many, many styles of music.

Similarly Pratchett is technically a fantasy author but some of his books are actually crime/detective novels, sci-fi, even romance.

Many people who say “I only read fantasy” are quite surprised when you point out many of the Guard books are just straight detective stories; similar to how many people are shocked to realize that Blues Brothers, is at heart, a musical.