* There's a great video of O-Sensei leading warmups before class. He's going through a series of exercises. About half the class is following along, some in sync, some not. The rest of the class is doing their own exercises, horsing around, random stuff.
I've been in a lot of classes in the US where the non-Japanese instructors were insistent that all exercises be performed in the same time and in the same directions - never had it happen even once in Japan.