I have also managed to established an SPP connection when Disconnecting the device from the bluetooth menu, while simultaneously creating an RFCOMM connection, which managed to stay connected and streaming while the device was actually appearing "disconnected" at the OS level. There may be something at the OS level blocking the RFCOMM service entirely.

I worked with Apple Bluetooth Engineering staff to restore connectivity to our device. As of Monterey 12.3 Beta 4, RFCOMM handles for our device are being properly return and connectivity is restored within our application. As an additional note, calls to IOBluetooth.recentDevices which we were leveraging are not currently working (at least for us). We have reverted to using IOBluetooth.pairedDevices() instead, which provides similar information.