Update: apparently this is not a bug. According to Amit Kumar Yadav "these are product internals and not exposed outside. However, I can tell you that this is not a defect.".
I was digging around the AppFabric Caching assemblies using Red Gate’s .NET Reflector today. I think I may have found a bug in a send/receive timeout that is getting setup in the WCF Transport Channel. The internal class Microsoft.ApplicationServer.Caching.WcfTransportChannel. In method SetupTimeouts, the SendReceiveTimeout is getting set to two times the send timeout value. I think it should be set to the send timeout + receive timeout. See the attached photo below. What do you think?