It is obvious if someone tackles and hair gets in the way vs grabbing/yanking someone down by the hair. Thats like with facemasking - there is difference between grabbing by the facemask and the facemask touching you.
The first year of the ban, only two penalties were called by referees for the horse-collar tackle. Owners voted 25–7 in 2006 to expand the rule to include tackles by the back of the jersey in addition to tackles by the shoulder pads.