I think that teaching a new student a leg lock makes about as much sense as teaching them a flying oma-plata. Once someone gets some experience its okay to teach leg locks I learned most leg locks as a white belt but i learned to defend them first which was a nice touch because you learn the effects of the holds and get a good understanding of the fundamentals of them. But even as a whitebelt i never spent much time on leg locks because when could you use them in a tournament? so what was the point. Now that I've advanced knee bars and toe holds are my bread and butter and i get to use them in tournaments so its great.