Product Categories Selectable Only By Admins

I am trying to created in the store a area where we display products "approved by the admin", product that we recognize the quality like a "Editors Picks".

The first idea that come to my mind is to use a category to this. When we (admin) find a product that we think that are good, we put this product in the category and to avoid that vendor use it, we make it unavailable under vendor plan setting.

What is happening is that if the category is not available in the vendor plan setting, I as admin cant add this category to that product. Is this a bug or it is working as expected?

Just for a better explaining, when you is an admin working in a vendor product you can select a category that is not available in the vendor plan, however once you save the product, the category disappear.