Of course it works. But what do you mean by that question? You need to determine what the purpose of this product is. It might only be to make sales, and nothing more, so it still "works".
Chalk is all the same. It just forms a coating on the outside of the hair, and will make the hair appear another colour. But if the hair is very dark, it shows through, so you may need to put a lot of chalk on the hair.
Because it coats the hair, it can feel rough and "dirty" since it is small particles of chalk dust on the hair. The hair will not have any shine. It does rub off, like chalk does, and washes off (or should) in the next shampoo.
Think about it carefully, give it a try to see how you like it, but it won't change your hair colour as a proper tint will. They are both very different things.