REST customHeaders config option not working?

I’ve gotten the customHeaders config option to work under the webui configuration (subject to the restrictions listed in the manual), but I have been unable to get it to work as well under the rest configuration. We’re getting a CORS violation in a different web app that is trying to call the REST interface and despite what the manual says (section 21.10 of the 6.0 manual), when I try adding the customHeaders tag, it seems to be ignored and does not appear in the headers returned. Bug or am I missing something else obvious here??!?

Is the issue happening with operational data only? There was a bug ((Issue tracker: #23039) concerning custom headers not appearing in oper data REST responses that has been fixed in ConfD 6.1.3.