Permanently disable hands free telephony windows 11?

Wireless headphones usually all have issues with lower audio quality when transmitting Mic audio at the same time as receiving desktop audio.

That's a bluetooth bandwith issue.

There's multiple threads about it online, e.g. https://www.reddit.com/r/techsupport/comments/44sxms/bluetooth_headset_goes_to_low_audio_quality_when/

The only workaround for this is to do as you've been doing, disabling the headset variant.
This will disable the headset microphone.

Why your thing re-enables on reconnect, I couldn't tell you.
You are navigating "Settings - System - Sound - "device" properties"
and then clicking the "Don't allow" button?

When the button says "Allow", the device is disabled.

Some headsets use two separate channels for "game" and "communications".
They generally use a dedicated USB dongle for connecting to the unit.
If your headset presents as two separate sound devices in sound settings, try to set the "high quality" as the default for sound, and the "low quality" as default for communications.

Another possible help is in the Windows settings: "System - Sound - More Sound Settings - "Communications" tab".
Ensure that Windows doesn't reduce other sounds on "communication activity".