Independent from whether or not this particular opportunity was a "sweatshop": you mention that you sent a list of web sites you've created and applications you have in Apple's App Store, but I didn't see anything in there about "code." Absent any actual code (not counting HTML, and assuming the web sites you mentioned weren't primarily JS) I'd certainly ask you coding questions as well.
EDIT to add reasoning: I've seen people that can release applications and put up web sites, the code for which is unreadable, unmaintainable garbage. I'm really happy to see that you can ship, because that is important, but if we're going to be coding together I also need to see that your code is passable.
That is a good argument to ask candidates to complete a written code test or to share their github page. That's still a bit different from quizzing on textbook concepts, but I will yield in the argument that a well-rounded engineer would probably be able to spout out answers to random CS trivia questions as well.
EDIT to add reasoning: I've seen people that can release applications and put up web sites, the code for which is unreadable, unmaintainable garbage. I'm really happy to see that you can ship, because that is important, but if we're going to be coding together I also need to see that your code is passable.