Thanks this really impressive video!
This plugin can handle predefined tab types. You have to define tab types first, in the “Product tabs” menu. It can be specified here if a tab type is applied for all kind of products, or only for products of selected product categories.
When you go into product editor page, you will find fields for all predefined tabs. You cannot create new tabs on product editor page, only the predefined tab content fields can be used, by entering content into them.
According to the video, you have not got any Product tab defined, that is why you cannot find any tab content editor field on the product editor page.
So this is the normal functionality. If you create one or more tabs in “Product tabs” menu, you can use them in product editor page.
I hope this is useful for you.