You and I can go back and forth on how the other is wrong by providing various internet links. I'll start:

"Mobile devices, the researchers conclude, listen to conversations through microphones and create personalized ads based on what the person wants or has done." [1]

"This passive listening ensures the virtual assistants are ready to help you with a task when needed. However, depending on the developer, voice tech apps may also use your conversation data to recommend ads and content. For instance, Google uses Assistant conversation data to personalize ad and content recommendations. Others, like Apple’s Siri, claim not to use conversation data to build marketing profiles or curate ads." [2]

But this exercise will actually produce less fruitful results because it's possible to prove anything via the online "research" nowadays. So let's try a different tack- thinking for ourselves.

FAANG are extremely notorious brokers of data. Everything about you and your browsing behavior is collected. I hope we can agree on this. Then why on earth would your conclusion be "they don't broker or process our audio data"? You'll have to have something better than it would consume battery life or would leave an identifiable trail of bytes, both of which could be mitigated by some clever programming.

Much better to have the hypothesis (hence "pretty sure") that they do, and then scrutinize. Until something definitive comes out that they absolutely do not, it's much more solid ground than a conclusion that you can simply trust these large corporations.

[1] https://dobetter.esade.edu/en/phone-listening-personalized-a... [2] https://us.norton.com/blog/how-to/is-my-phone-listening-to-m....