The question is still open. I need to find answer on how I can decide (based on serial number of device) whether second or next device can be handled by driver. In IOKit I just had to overload IOAudioEngine::getLocalUniqueID and return empty OSString if I didn't want the driver to handle another device.

Problem is solved. It is possible to give UID to init function of IOUserAudioDevice.

Thank you for response. I've already reported it through Feedback Assistant - bug FB9778734. It is open and I am waiting for response.