Huh? Google already controls the entirety of the Phone app — if you're convinced they want to eavesdrop on your calls, they certainly don't need you to enable this feature to do so.

Also, the post states this is done completely on-device and links to a page with significant details on this: https://support.google.com/phoneapp/answer/10104618

The privacy concerns of Google doing nefarious things with tinny renditions of elevator music? And it's an optional feature that you explicitly have to activate each time to boot.