Kahn tested his system on XETRA - The Mighty 690, in the 70s. I could hear the station in Portland, after CBU left the air. If you tuned one radio slightly left of the center channel and the other, slightly right, you got stereo. I tried it once and thought at the time that it sounded like FM stereo, with the door closed.
KING 1090 in Seattle ran the Kahn ISB system for a few months. Just like most AM stereo systems, it sounded unique, but just not comparable with FM stereo.