URLs set to include categories and sub categories, but still the shorter URL are viewable

[rob_wood1]

Hi 

We have set our store to be Use Categories Path for Product URLs: Yes

And it works

So I have www.mydomain.com/category/sub-category/my-product

But if I remove category and sub-category, so I am left with a URL like this: www.mydomain.com/my-product

So I am confused, as I thought choosing to have cateogies in URL would remove the shorter versions?

And if this is an issue we need to set up redirects from short to the longer format URL?