UPDATE: Sep 25, 2020:

• The bluetoothd (aka Bluez) version remains at 5.5 in RPi OS buster

• The date stamp at the bottom of man bluetoothd still has a 2004 date stamp

• The list of Bluetooth-related man pages for buster is here

• The quality of the Bluetooth documentation for RPi still sucks.

That is all.

Please feel free to edit this answer, or comment if you have better information.

UPDATE 1: Sep 25, 2020:

• The bluetoothd (aka Bluez) version remains at 5.5 in RPi OS buster

• The date stamp at the bottom of man bluetoothd still has a 2004 date stamp

• The list of Bluetooth-related man pages for buster is here

• The quality of the Bluetooth documentation for RPi still sucks.

That is all.

UPDATE 2: Nov 2, 2020:

Still no improvements on the documentation AFAIK, but I did make some (painful & slow) progress on getting Bluetooth to do something useful on my system - streaming music to a BT speaker.

Please feel free to edit this answer, or comment if you have better information on the documentation.