I work for an un-named company that makes stuff that has google assistant on them. Initially we out hardware mutes and pipes the microphones to physical hardware that monitored for wake up words and would then start piping the microphone data to the mother ship. Google told us to stop that, only way to certify the product as compatible with Google Assistant was to pipe the raw microphone data to the mother ship 24/7. That was 5 years ago and I removed all devices from my house.