I bet combox is a condensed way of saying (tele)com(munications) box. Connections made are made through the phone, all bluetooth does is to show the phone menu on the screen and route the audio through the car speakers and microphone. A 2012 car uses 2G, which is no longer supported by BMW, so BMW teleservices won't work.
https://www.cnet.com/roadshow/news/b...ed-telematics/
iPhone connectivity is always hit or miss. Apple operates in a vacuum, they never worry about how their gear will interface with other technology. Sometimes when bugs are found and enough people complain about it they'll fix them, but not always by a long shot.