Multipoint connection isn't working well with the io-12 for me. Is erratic. I'm using iPhone 15 Pro (iOS 17.1) and 16" 2021 MacBook Pro (Sonoma macOS 14.1), both devices with the more recent firmware updates.
Connection to both devices is very, very quick when you first switching on the headphone. BUT after you pause first device and play the second device, the music is playing fine and very quickly in second device, BUT when you want pausing or playing or playing next/previous track from the headphone controls in the second device, the device isn't responding anymore BUT you can looking at the first device and seeing that is pausing or playing or playing next/previous track but with no sound (the volume control is always working fine in the 2 devices, by the way). So, you must doing all this actions manually directly in the second device's playback functions or use ONLY one device for things becoming normal operation from the headphone.
This happening equally if I starting using my iPhone and then going to my MBP, or if I starting with my MBP and then going to my iPhone, always the second device will playing quickly after switching but then not pausing or playing or playing next/previous track from the headphone, only using the second device's playback controls.