If somebody steals your car/purse/whatever with an airtag on it, and that person has an iPhone, will they get notification that somebody is tracking them?
"If a Find My network accessory that's separated from its owner is seen moving with you over time, this alert is displayed"
In my experience, it's generally more than the few minutes someone that grabs a purse will keep the purse before looking for cash/whatever.
A car is, of course different. I had the brilliant idea to put an airtag in my car so I could find it if I forgot where I parked. Then I got a call from a very worried SO that borrowed my car that thought they were being stalked (there's a history there of issues, so yeah, fun times).