Either AddressComponent.types Array<AddressType | GeocodingAddressComponentType> should have a type added I just recieved from google geocode endpoint. "postal_code_suffix" which is the last 4 digits of a 9 digit US post code.
In json the response include:
{
"long_name": "4961",
"short_name": "4961",
"types": [
"postal_code_suffix"
]
}