I noticed that today. It's like the car mutes the audio/music response (audio vol controls linked?) for her Ding acknowledging she's listening, then if the response is long enough it is beyond the audio reduction expiration window and music comes back (if playing previously) with her talking at...
For me, those adjustments are showing the Alexa icon while adjusting (also tried them from the main screen controls vs scroller while active) but it only changes the acknowledgement/ding sound.
Phew, I'm not crazy! Picked up my used new to me R1T in Normal yesterday and couldn't figure out how to fix her voice response volume during my drive home. The wakeup noise was the only thing changing.
I'll start out my ownership path with a bug submission ;p