EWS Managed API ExtendedProperty PidLidResponseStatus gives String instead of integer like it is defined

Since Exchange 2016, the extended property PidLidResponseStatus gives Strings. But it is defined as MapiPropertyType.Integer: Here is how it is defined:

ExtendedPropertyDefinition PidLidResponseStatus = new ExtendedPropertyDefinition(DefaultExtendedPropertySet.Appointment, 0x00008218, MapiPropertyType.Integer);

https://msdn.microsoft.com/en-us/library/office/cc839923.aspx

Is this a Bug in Exchange EWS?

At the Moment I am using this workaround:

 object propval = null;
 if (sourceitem.TryGetProperty(PidLidResponseStatus, out propval))
 {
    try
    {
       isMeetingDeclined = (int)propval == 4; //  olResponseDeclined
    }
    catch (InvalidCastException)
    {
        // Bei Exchange 2016/Office 365 leider als String
        /*Unknown  
        Organizer  
        Tentative  
        Accept  
        Decline  
        NoResponseReceived */

        isMeetingDeclined = ((String)propval == "Decline");
     }
 }

Is there somebody who knows something about it? Or is there something I am doing wrong?

This is the Soap response:

 <m:GetItemResponseMessage ResponseClass="Success">
<m:ResponseCode>NoError</m:ResponseCode>
<m:Items>
  <t:CalendarItem>               
   <t:ExtendedProperty>
      <t:ExtendedFieldURI DistinguishedPropertySetId="Appointment" PropertyId="33304" PropertyType="Integer" />
        <t:Value>Organizer</t:Value>
      </t:ExtendedProperty>
  </t:CalendarItem>
</m:Items>
</m:GetItemResponseMessage>