I wrote a huge answer and it got deleted. In short the Shadow Tag users themselves don't have the same affect in LC as OU. In OU Shadow Tag created a big problem with Stall as after certain things were checked Stall became impossible to deal with as a result of Shadow Tag. In LC, Gothita is a fast and frail revenge killer and Wynaut isn't bulky enough with it's super subpar stats. They aren't cut for gamebreaking stall and thus don't have the same effect.