Hi there,
But what does: "This process will try to preserved field data but there might be data loss if there are no matching field between 2 categories" means?
This is precautions alert for you as this switch might lost your data for your category as might be your new category have less field than before.
For example, previous category got address field, but your new one doesn't have address field. And those field will be lose and follow your new/latest category. Hope this clarify it