Why double auth call on server pages?

export default async function Home() {
  const hello = await api.post.hello({ text: "from tRPC" }); // this calls auth internally also
  const session = await auth();

  if (session?.user) {
    void api.post.getLatest.prefetch();
  }

  return (
    <HydrateClient>
    //page
    </HydrateClient>
  );
}