That makes sense, but isn’t it assuming they’re processing data on the device? I would expect them to send raw audio back to be processed by Google ad services. Obviously it wouldn’t work without signal either, but that’s hardly a limitation.
As someone else pointed out, how does the google song recognition work? That’s active without triggering the light indicating audio recording, and is at least processing enough audio data to identify songs.
It’s a reasonable explanation, and what I typically assume to be true. Still, I’m curious about the actual mechanics, and if it potentially could be being done by Google without the larger tech industry being aware of it.