GSON only needs to reflect based on fields: 4d942db168/gson/src/main/java/com/google/gson/internal/bind/ReflectiveTypeAdapterFactory.java (L152) There's no reason to disallow optimizing methods.
4d942db168/gson/src/main/java/com/google/gson/internal/bind/ReflectiveTypeAdapterFactory.java (L152)