Just because something is free doesn't mean you can just assume and then complain because it wasn't what you thought it was.
There are select people who also make that assumption, and it has nothing to do with searching terms and conditions. It is all laid out very easily and it is clear to see in marketing, any readily available documentation on the service as well as the fact the it clearly shows what is available in the Apple TV Plus service when in the app. Also, when one goes to claim the offer they would have to navigate there anyway where they can very easily browse what is available.
Hulu has a select library of programming and that is a promo price. It doesn't have anywhere near what iTunes offers, plus the selection from other Apple TV channels. All of which you were expecting to have access to here.