Can someone explain conversation groups in service broker?

Currently, I'm using service broker to send messages from one SQL server to another. On the sending server, I'm trying to correlate the messages so they are processed in serial on the receiving side. Based on the documentation, conversation groups seem to be a perfect fit for this, but on the receiving server, the messages get assigned to a different conversation group from the one I specified when sending the message.

I've search around the web and saw that this behavior seems to be intended (http://social.msdn.microsoft.com/forums/en-US/sqlservicebroker/thread/baf48074-6804-43ab-844a-cb28a6dce02b/), but then I'm confused about the usefulness of the syntax from (http://msdn.microsoft.com/en-us/library/ms178624.aspx)

WAITFOR( 
  GET CONVERSATION GROUP @conversation_group_id FROM [dbo].[ReceiveQueue]
)

If the conversation group doesn't come across with the message from the sender and messages sent with the same conversation group id don't have the same conversation group id on the receive side, what's the point of the code above?