Same here. I opened a support case and got a response: I have verified with development and this seems to be by design not to show pieces of information to existing WHD client cc recipients. As it is the design, I can however submit a feature request asking that they consider adding that information to those recipients.
If you try to cc an email address that is NOT already a WHD client on your system, the custom template works fine for the cc person. I think it's a bug but they call it a feature.