Radio Does Not Mute for Nav Spoken Directions- 2016 Avalon Limited

Subject says it all.
The Entune radio in my 2016 Avalon Limited does not mute when the factory Nav system gives spoken turn by turn directions- thus making
them hard to hear/understand them.
Dealer can't fix and Toyota USA says this feature is not available on their technically and electronically advanced top of the line flagship sedan.
On most cars I've driven, the radio mutes for spoken directions on a factory nav. Does yours?
Are they feeding me a line-- or did they drop the ball when they designed the system?
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