UW is not always money like a lot of people think it is. I suppose the reason why people only rely on questions to study as a primary source is that there really is no time for most of us during clinicals to power through a comprehensive set of review books. A single question bank cannot cover every topic. There are still loopholes in UW. You just have to do your best by supplementing. In order for a Question bank to cover everything, you'd need to do like 10,000 questions just to cover all possible topics inside and out.
The best sampling of how the real test looks like is the sample test that USMLE puts on their website. Don't misinterpret what I just said and think that the USMLE sample exam is a good predictor, because it's not. I just I found my real exam to be similar in depth and difficulty (and simplicity) as the sample questions. NBME 4 was hard (I actually failed the form 4, did well on forms 1,2,3). I haven't gotten my score yet, but I feel like the test wasn't all that bad. Of course there will be questions that are WTF, but that is expected in any test.