Can there really be an objective measurement? You should think first thing data harvesters would implement is a sort of cloak, to erase any traces of what’s going on. Think Dieselgate, but more sophisticated. E.g. phone detects it’s being tested the way you described, or is in the hands of a state attorney or whatever, the recording/ forwarding/ prcoessing of data stops.
I just find it nifty that I can slide in a graphics card and use it as an add-on processor, just like the Amigas of old did, and add capacity for some tasks even when the CPU is already at 100% doing something else entirely. Just love hearing the sound of all fans spinning up at the same time.