Unfortunately, what the article described sounds a lot like a thermometer coded delta-sigma DAC or other similar design. How these are constructed and used are

Unfortunately, what the article described sounds a lot like a thermometer coded delta-sigma DAC or other similar design. How these are constructed and used are well known, and they're probably lying about "closely guarded" to make sure people don't realize it is just a clever usage of an off the shelf part, and none of the magic is in-house.