189yds is not a mid iron for the majority of golfers. Check out the charts for distances according to h/c and for most golfers it is nowhere near that.But that kind of shape makes good sense for a mid iron which is what the length is what it is, I don't know what all the copies are but I bet there aren't many where the back tees are less than 170 yds.
That design is about hitting one side of a green, the ball funnelling down (I watched the 'Watch with Ken' video ). Not middle or either side, one side only. Length isn't the big factor in that. It's about a precision shot.