why does auth encrypter with dir have a key wrapper?

gistfile1.txt

https://github.com/decentralized-identity/veramo/blob/next/packages/did-comm/src/encryption/a256kw-encrypters.ts#L144-L157

export function a256gcmAuthEncrypterEcdh1PuV3x25519WithA256KW(
  recipientPublicKey: Uint8Array,
  senderSecret: Uint8Array | ECDH,
  options: Partial<AuthEncryptParams> = {},
): Encrypter {
  return createFullEncrypter(
    recipientPublicKey,
    senderSecret,
    options,
    { createKek: createX25519Ecdh1PUv3Kek, alg: 'ECDH-1PU' },
    a256KeyWrapper,
    { from: (cek: Uint8Array) => a256gcmDirEncrypter(cek), enc: 'A256GCM' },
  )
}

https://github.com/decentralized-identity/veramo/blob/next/packages/did-comm/src/encryption/a256gcm-dir.ts#L8-L42

function createA256GCMEncrypter(
  key: Uint8Array,
): (cleartext: Uint8Array, aad?: Uint8Array) => EncryptionResult {
  const blockcipher = new AES(key)
  const cipher = new GCM(blockcipher)
  return (cleartext: Uint8Array, aad?: Uint8Array) => {
    const iv = randomBytes(cipher.nonceLength)
    const sealed = cipher.seal(iv, cleartext, aad)
    return {
      ciphertext: sealed.subarray(0, sealed.length - cipher.tagLength),
      tag: sealed.subarray(sealed.length - cipher.tagLength),
      iv,
    }
  }
}

export function a256gcmDirEncrypter(key: Uint8Array): Encrypter {
  const enc = 'A256GCM'
  const alg = 'dir'

  async function encrypt(
    cleartext: Uint8Array,
    protectedHeader: ProtectedHeader = {},
    aad?: Uint8Array,
  ): Promise<EncryptionResult> {
    const protHeader = encodeBase64url(JSON.stringify(Object.assign({ alg }, protectedHeader, { enc })))
    const encodedAad = fromString(aad ? `${protHeader}.${bytesToBase64url(aad)}` : protHeader, 'utf-8')
    return {
      ...createA256GCMEncrypter(key)(cleartext, encodedAad),
      protectedHeader: protHeader,
    }
  }

  return { alg, enc, encrypt }
}