Not confusing at all b/c all the sounds are laid out for. I used this for my 6year old Dd and am now teaching my DS who is almost 5 but really wants to read and he asked me to get the book for him.
He is already reading the short sentence stories.
I don't think it will be confusing either for the child. I figure that once in a while dh is going to do a lesson with one of our girls with 100EZ, and honestly I'll welcome the break as much as the girls will. I've learned long ago that if she isn't getting something with me to have dh do the lesson because she'll just magically get it.