Funny thing happens when someone pulls their arm back from you. Depending on which way they are turning their arm - inward or outward - they tend to lean forward or backward. Thus, we have two things that tori is often able to follow that retracting arm into - udegaeshi (#7) and udehineri (#9). In udegaeshi uke retracts his arm, rotates it outward, and leans back. In udehineri, uke pulls his arm back, rotates it inward, and leans forward, creating that gem of a technique in every martial art - the bar hammer lock. In Judo it is called udegarami. In jujitsu it is called the Kimura. Tori's job in this technique is to find a way to safely follow the arm to it's final resting place and hold it there to maintain uke's forward leaning posture and to provide leverage to make uke move in the desired direction.
In our kata version everything is done with uke's arm very tight against uke's flank with the wristlock pressed against uke's butt or lower back. This is actually a safety measure for uke. With the arm in this position, uke's body is actually splinting the arm so that it is difficult to accidently break the arm before uke can roll out of the technique. Later variations in the koryunokata execute the technique with the arm away from uke's body. This requires a gentle tori and a skilled uke because this position is a recipe for disaster for uke's rotator cuff. This is a feature of the hineri position of the arm - it isolates the smalest muscle in the rotator cuff and places tori's and uke's weight against it.