If someone slips an AirTag in your car to stalk you, your own phone would enable your stalker because by default it would automatically update the location of the AirTag, even if you are not an AirTag user.
It is a bit different if your stalker used Tile to track you. You'd have to download that app and opt in.
The problem is that there is some benefit in integrating almost any service into the growing Apple ecosystem and almost any product could conceiveably benefit from become an Apple feature. I think regulators need to draw the line somewhere to protect competition.
