"Beep as anti-stalking measure" is somewhere between marketing spin and gaslighting. A lost AirTag chirps to serve its primary function of being recovered.
The timer is 3 days[1], which observers (Forbes, WaPo) agree is surprisingly unreasonable for this use case. We can infer it was never a serious design consideration.
On Android, decent Bluetooth is a gamble, but scanning will theoretically find one[2].