One of the more obvious reasons that one would embrace the ribs is to protect them from strikes. When the ribs are not embraced or the elbows are flared out or the fists put in unusual positions this has the effect of changing the angle of the elbow relative to the fist. This changes the angle of the “arrow”. When your elbows are flared , you have to correct the flare before your blow can be effectively launched. It is both a waste of time and a dispersion of power. When it is properly embraced then it is more centered and prepared to make an effective attack or counterattack. Many practitioners simply think of the variations as differences in style without considering the effect on practical function.