Most phones these days use randomized MACs

https://www.guidingtech.com/what-is-mac-randomization-and-how-to-use-it-on-your-devices/

Not sure if that is for BT too, but looks like there is some support for it in the standards

https://novelbits.io/how-to-protect-the-privacy-of-your-bluetooth-low-energy-device/

https://novelbits.io/bluetooth-address-privacy-ble/

The recommendation per the Bluetooth specification is to have it change every 15 minutes (this is evident in all iOS devices).

So seems like it is implemented on some phones at least

https://www.bluetooth.com/blog/bluetooth-technology-protecting-your-privacy/

From 2015. So this seems to be a solved problem for a decade now