It's not so, its encrypted, no one get an alert but you, and whoever you authorise, Paint it like a bitcoin.... no one will take it then
Not true, If your iPhone detects an apple tag that is "travelling with you" but is not yours, you will get an alert on your phone. So as a thief with an iPhone, you steal a car with a tag in it, your phone will tell you of the tags presence in the car. (Apple doesn't know you are nicking a car, so it assumes that someone has put a tag on you without your knowledge (the tag is not registered to you so it knows it's not yours)
Once you find the tag you can then follow hand instructions on your phone to disable it, because after all Apple prides themselves on ease of use :)
see
https://www.apple.com/uk/newsroom/2021/04/apple-introduces-airtag/ under privacy and security which says
"AirTag is also designed with a set of proactive features that discourage unwanted tracking, an industry first. Bluetooth signal identifiers transmitted by AirTag rotate frequently to prevent unwanted location tracking. iOS devices can also detect an AirTag that isn’t with its owner, and notify the user if an unknown AirTag is seen to be traveling with them from place to place over time. And even if users don’t have an iOS device, an AirTag separated from its owner for an extended period of time will play a sound when moved to draw attention to it. If a user detects an unknown AirTag, they can tap it with their iPhone or NFC-capable device and instructions will guide them to disable the unknown AirTag. "