I too recently read that and wondered on the same. I was just on the verge of trying protocol rtp audio, for Cisco VoIP phones, but the "need" got eliminated, so, unfortunately, I didn't find out. If protocol rtp audio didn't work, I was prepared to next try protocol rtp.
In your reference, right above that note, mention was made it works if audio is related to SIP (which would have also been true for me).
I too hope others post a response.