I think the issue with Faulk and Parayko when it comes to #1 designation is this:
What does #1 even mean? Some mean as long as you are in the top 32 defensemen, then you are a #1 guy. It's logical, but not something I really agree with. Usually when we say #1, we are mostly talking about the more elite guys that can handle any situation and anchor a top pair that can go against top lines, regardless of their defensive partner. Usually, it's much closer to 10-15 of these guys in the league, maybe a bit more, but it's not simply taking the top 32 guys. Parayko and Faulk both fall just short of this as they either need a particular deployment, a certain type of partner, or have certain limitations in their games.
Another thing that sort of unfairly hurts Faulk is that he'll ultimately be with Krug, and that limits how that pair can be deployed defensively. In an ideal world, he's with another Leddy type that is great at moving the puck, competent in the offensive zone and still good enough defensively where deployment isn't as big of an issue as it is with Krug.
That's why Faulk and Parayko are basically 2 sides of the same coin, we need both healthy together and that can give us both sides of a #1, but if one gets hurt, then we lose 1 and the other becomes less effective.