I also think it was recorded the way you describe it with mono microphones on all the individual instruments hard-panned left or right.That's another sign of being close miked and panned into position. The album was recorded at the Village Vanguard, NYC. 1962 would still be relatively early for stereo recording of a live date.
But there's one thing I'm not sure about, did they duplicate and blended in the piano track to the left side as well? If so, the person who did that was really smart and a bit ahead of his time, because as we all know, in the early days of stereo recordings they only had L-C-R panning, nothing could be panned "almost all the way to the right".