I think the top 3 criteria for this list are:
1) How good is the starter
2) How likely is the starter to play every game this season
3) How good is the backup
Good starter w/ high likelihood to play every game = high on the list.
Good starter w/ good backup = high on the list.
Ravens have (in the NFL's eyes) a decent starter, who is decently likely to start every game (but after the beating he took last year, even though his track record says he's never missed a start, these guys probably think there's a decent chance he could get knocked out of the season at some point), and we have a sub-par backup (they even say in this article that Taylor is OK as a gadget for us, but is unproven and unsure whether he can be a good starter if Flacco goes down).
I guess it's an expected placement on the list given how we know the NFL views all of those qualities about our QB situation right now.