I think you'll find it's not so much about how likely the event is (stalking vs theft) as it is about the potential impact of the event.
The things you want to "protect" with an invisible AirTag are, at their core "just stuff".
The things being protected by not selling an invisible AirTag are, at their core "people".
I think if my car is stolen, it's probably a bigger deal for me personally than stalking.
I'm not a female, so I don't anticipate a civilian stalking me for really any reason. A non-civilian wouldn't use an airtag.
Zero stalkers are stopped because of airtag policies, since many other devices exist.