Google is part of the public. Yes, this would depend on the interpretation of the court, but the point is that the expectation of privacy no longer exists when you are explicitly sending that audio to a 3rd party.
> Law enforcement must have a valid and legal warrant
Kyllo v United States established a bright line test that the need for a warrant specifically depends on if the technology used is commonly available to and used by the general public.
At some point it is impossible to know the list of possible words you cannot speak and the public will simply start assuming that they may be recorded anyway. When that perception changes, so will legal doctrines.
You can own every single smarthome device in existence today and quite rightly assume that you are not being passively recorded. These concerns amount to overblown FUD.