They have this feature but closing the lid on a MacBook or even putting it to sleep allows Bluetooth devices to stay connected. Heck, a MacBook even while in sleep mode will connect to Bluetooth devices. As far as I can see, this requires a third-party app to fix. Can an application still use the microphone on a Bluetooth device that’s connected?
This has to be the most annoying thing in MacOS. My laptop, soundly sleeping in my backpack, takes over my bluetooth headphones all the time.
I don’t think I’d recommend the preference to anyone who doesn’t already/still share it. But it’s a blissful quiet.