How is the bthkd extension library used under WinDbg?

Question

I am trying to use the !bthtree command to dump the complete Bluetooth device tree as specified from the !bthhelp command.
WinDbg is running and is attached to a svchost.exe process that imports several Bluetooth DLLs:

• svchost.exe (1808) | DLL | C:\Windows\System32\bthserv.dll
• svchost.exe (1808) | DLL | C:\Windows\System32\BthTelemetry.dll
• svchost.exe (1808) | DLL | C:\Windows\System32\Microsoft.Bluetooth.Service.dll
• svchost.exe (1808) | DLL | C:\Windows\System32\Microsoft.Bluetooth.Proxy.dll
• svchost.exe (1808) | DLL | C:\Windows\System32\Windows.Internal.Devices.Bluetooth.dll

Using the !bthkd.bthtree command results in the following message:

Controller: Failed to read list of device objects.

BTHENUM: Error: Unable to read BTHENUM!BthEnumGlobals Unable to find driver object

RFCOMM: 00000000: Unable to get value of ObpRootDirectoryObject Error: Unable to read rfcomm!g_DriverObject

ENUMERATED DEVICES: Error: Unable to read BTHENUM!BthEnumGlobals Unable to find driver object

Sadly the other !bthkd commands (such as !hcicmd, !bthenuminfo) also fail in a similar manner. WinDbg is debugging the target process locally.
Unfortunately, the documentation (bthkd) does not really provide much additional information on how to use the bthkd extensions.