Bluetooth Classic in Bluetooth Core Specification through 5.3 does not properly conceal device information for Bluetooth transceivers in Non-Discoverable mode. By conducting an efficient over-the-air attack, an attacker can fully extract the permanent, unique Bluetooth MAC identifier, along with device capabilities and identifiers, some of which may contain identifying information about the device owner. This additionally allows the attacker to establish a connection to the target device.
https://www.computer.org/csdl/proceedings-article/sp/2023/933600a521/1He7Yja1AYM
https://www.bluetooth.com/specifications/specs/core-specification/