The process involved just asking a bunch of technical trivia questions about .NET, ASP.NET Webforms, MVC, JavaScript and SqlServer. They weren't interested in discussing experience, troubleshooting ability or anything that would serve as a good indicator of whether someone could succeed in the position. It's sort of like choosing your next lawyer solely based on how well they could recite back every law in their law school books.
Sure, technical questions are important and should be asked, but the other piece to this is that code should be written, a homework project should be completed, and subjective questions should be asked. Ultimately, is this someone who has skill, experience, passion, and shows the ability to learn and pick up concepts quickly.
Because a full stack developer has to deal with such a large amount of languages, frameworks, and concepts it's simply a situation where one has to brush up on relevant technologies as they use them for a particular project.