Pourquoi un return type discriminated union est meilleur que { data: T | null; loading: boolean; error: Error | null } ?

type QueryResult<T> =
  | { status: "idle"; data: undefined; error: undefined }
  | { status: "loading"; data: undefined; error: undefined }
  | { status: "success"; data: T; error: undefined }
  | { status: "error"; data: undefined; error: Error };

function useQuery<T>(url: string): QueryResult<T> {
  // implementation
}

const result = useQuery<User[]>("/api/users");

if (result.status === "success") {
  result.data.map(u => u.name); // TypeScript wie!
}