Yes, this should be hidden. Please check the followings:
– if this tab content is absolutely empty in the product edit page, so is must not contain any space, tab or other not visible characters
– also check that Default Content, Content Header and Content Footer fields are absolutely empty on the “Accessories” tab type in the “Product Tabs” menu.
A tab is hidden only if does not contain any character. It works for us without any problem.
I hope this is the cause of the problem.