EZ-Feed vs EZ-Set
Simply put, rotation. Larger bars have more mass and hence, more inertia than smaller bars. Non-rotating smaller bars, when introduced to the grinding operation, quickly accelerate in rotational speed which then matches the rotational speed of the grinding/regulating wheels. Large bars, due to their inertia, do not get up to speed as quick. When these larger bars meet the grinding wheel potential damage can occur due to the difference in speed.