The metrics simply correlate with accident rates. For example, your premiums increase if you drive late at night, which does not mean that you are a bad driver. Their metrics also do not punish you for accelerating aggressively or driving at high rates of speed (only if you turn too fast or hit the brakes too hard, but if I slam on the brakes in the name of safety, or perform an evasive maneuver, does that mean I am an unsafe driver?)
Also, it’s worth pointing out other insurance companies have a solution for this that has worked for decades. If someone proves they are an unsafe driver by receiving a infraction or filing a claim, then you adjust the rates. No need to spy on the person with invasive amounts of data, or use arbitrary metrics that use correlation instead of causation. But Tesla has to reinvent things that were not broken in the first place, like door handles (just replaced the door handle on a brand new model S because dust got in there LOL).