FWIW I think I've found the bug in Honda's code. When the Honda sends a "Service Search Attribute Request" for the "Audio Source" service on my phone it's omitting the UUID. The UUID is required. As a result, my phone responds with "Unknown service" and ends up transmitting all audio as generic data.

With the other devices I've tested, the UUID is there, my phone responds with the required information for the Audio Service, and all music gets streamed using RTP (Real Time Protocol).

On phone with Honda now.