> GACT works much more reliably and extensively than any other system based on either GPS or mobile phone location data (based on cell towers) would be able to (under normal conditions). I want to stress this point because some people have responded to this threat saying that this is something companies like Google (using their GPS and WiFi names based location history tool) can already do for years. This is not the case. This type of contact tracing really brings it to another level

I'm curious about this, the author says they would like to "stress this point", but then provides no analysis or evidence to impress this... anyone have any buttressing points?