Yet the same is true of IP addresses. You (typically) cannot know for certain whether traffic from an IP address was originated by a specific person and yet it's typically considered PII because it can be used in conjunction with other information to identify you.

Even your full legal name and birth date cannot be guaranteed to refer only to you specifically (as there could be someone else with an identical name and birth date), but it's obviously still PII because it helps narrow the field immensely if you can combine it with other information - for example, your IP address.

So yeah, "anyone could have been driving my car", but if you also know that the car drove from your home to your work then that narrows down the list of likely individuals immensely.

Conversely, if your license plate was spotted parked near an anti-ICE rally, then they can be pretty confident that you or someone you know was near an anti-ICE rally, which means they can harass you about it, follow you around, shoot you in the street, etc.