People like to point to Tannehill as a rookie success, debatable yes, but he did play well at times. However, the reason for the success he did have, I think , is that he had his coach from college calling the plays. That may be one reason for the bills coaching decisions.
Take a book from what the dolphins did, only do it better, and, hopefully, get a better result. This way you really give your rookie quarterback to tool to succeed right away. He can gradually learn a new offense(when necessary) while implementing what he knows. I don't know if this is the plan but that does increase the value of a pick, the ability to come right in on day one and run your offense.
So at 8 Nassib would be worth more because the development cycle would be nonexistent. IMO