Hi Douglas,
I had the same error and talked to an Cisco TAC engineer.
He told me the following:
No worries. Did a bit of a research and I see that jabber still doesn't support huntgroups. That's the official response. Of course that doesn't mean that nothing will work, it's just that the results will be unpredictable.
I know that this may come in the future but development doesn't have that planned for now. I believe that if you open an SR you will be told the same but if you want an official answer feel free to open a new SR.
You can maybe talk to the local cisco account team. They can go to the development and product management with enhancement requests from the field as far as I know.
Best regards
Ben