Well, I think I've worked out the culprit.
When at home Google Home is responding to "Hey Google" as expected but the phone is also responding "OK but for that you'll have to unlock the phone" as I had to disable the phone from responding when locked as both devices were responding most of the time, this is then showing the lock screen, so nothing nefarious is happening.
It seems that the setting doesn't totally stop it responding since it says to unlock the phone every time. The only solution would appear to be disabling the microphone but doing so manually will be bothersome. I can't find an option in Google Routines or Bixby.
There are apps that will block the microphone but does anyone know of one that can disable the mic except for phone calls but only when at a location or on a specific network? That way it would disable the microphone when I arrive home and enable when I leave. There was one mentioned on reddit 3 years ago but since all the apps are called "Microphone Blocker" having the name doesn't really help find it. Or is there a Bixby routine that I've overlooked?
