“Its only certain HD Radios which have C-QUAM AM stereo decoding but they are out there.”
My early Sangean HDT-1 tuner appears to…It sounds a little goofy, but it does switch to AM stereo after it has been tuned to KBPS for a few seconds.
If I were king, AM stations running IBOC would be required by the FCC to switch to C-QUAM at night!