Customize button enable if the product type = None

Hi All,

We have product structure like below

         Parent - A  ------------ Product type = Customize

            Child - C1----------- Product Type = None

            Child - C2------------Product Type = None

     

It is a vanilla customize button. I think Child - C1 and Child - C2 customize button should not be enable. but it is enable for us.

What could be the reason and why it is enable for product type = None? Is their any parameter setting we have to do?

Thanks in advance