Make it make sense…Stack Height of SPD pedals??

The Shimano Rally SPD pedals, are power meter petals. So they are understandably more chunky than the regular SPD pedals as in side by side photo.
But these chunky ass power meter versions are listed as having LESS stack height (13.5) , than the standard XTR version (15.1). I’m struggling to make sense of that.
As I understand it, these should use the same cleat so am I missing something??? Thanks in advance!