The TV specs say it has BT audio streaming but I think your phone doesn't act as a BT receiver but as a transmitter just like the TV. You don't need to use your phone anyway. Just pair BT headphones with the TV.
I have never ever seen a feature like that. I actually have an LG 4k tv (I think mine is the 65uh6500) and there is definitely no option to do that anywhere.
The TV specs say it has BT audio streaming but I think your phone doesn't act as a BT receiver but as a transmitter just like the TV. You don't need to use your phone anyway. Just pair BT headphones with the TV.