I find it pretty hard to ignore the role of deployment and linemates in this. He played what, less than 300 of his well over 1000 5v5 minutes without McDavid and/or Draisaitl on the ice? And in those minutes without those two, his numbers take a massive nosedive. Part of that, is just the Oilers depth being so lacking, and there's inevitably going to be drop-off there. But it's still a major factor i'm not willing to overlook. Not when it pretty much squares with my impressions in just watching a million Oilers games (this year, especially). And especially when we're looking at a one kind of wonky, and shortened season sample of Nurse appearing to "break out" in that role.
So no. I wouldn't say he's a true #1D. In the same sense that i absolutely would not have called Christian Ehrhoff a real #1D at his peak, playing those "top volume minutes" on a Cup Contender posting serious points and robust possession numbers - while stapled to the Sedins up front, and the corresponding type of minutes and deployment.
Doesn't mean he's not a great fit for that particular role with the Oilers, and one that they're going to continue to benefit from for a long time to come. Those types of defenceman can be an "engine" of a team on the back end. I'm just not really ready to call that a true #1 Defenceman. Not with reservations from watching him, about how he'd fare outside of that situation, and how much flattery is involved there. For me, a true #1D comes pretty much without qualifications.