Please correct me. But it simply cannot. There are black box binaries for their hardware that are not open. What is open is your ability to obtain them, but the source is not available. So the drivers for the camera and modem and whatnot are not sealed. I'm sure some have reverse engineered some of them but I have to assume (because I still hear stories of this) that many are still black box binaries.
And you aren't paying Google for that service that for you, so it is no different than using community tools to cleanse a Windows PC of adware and telemetry.