User blog comment:JBox2D/Yasuo, Ashe, the League of Mobility, and everything else that I think should be done/@comment-4996845-20140207022840/@comment-4996845-20140212234420

Actually a stun wouldn't interrupt a dash either, as it technically disables your control over the chamipion temporarily. The only way to stop a dash is through knockup/knockback, and that just doesnt feel right for Ashe's kit. That's the reason behind the "stops their movement" part.