If I remember correctly, a year or two ago the minors updated to a system that uses a rolling average of the batters height/stance over the past 50 ABs to draw the zone rather than height alone. So if two guys have the same measured height but one has a consistently lower stance, the zone adjusts for that:
"Hawk-Eye is now taking a snapshot of the hitter’s body position at the moment the baseball is midway across the plate (the same location used when evaluating umpire performance) and is then utilizing a rolling average of those snapshots across the hitter’s 50 most recent plate appearances to determine the hitter’s zone.
The zone is not dictated or impacted by a batter’s stance prior to the pitch being delivered, so hitters can’t artificially shrink their zone with a wider stance that compresses the gap between their knees and belt, nor are players who use a more upright stance punished with a larger zone for doing so."