Don't assume he's going straight to the NHL team, even if they might give him a (meaningless) game or three before the start of the playoffs. He's still a young kid, and he wasn't like a top 10 pick, so he's probably gonna be spending most of the next year or two in the AHL developing other parts of his game. Maybe they see parts of his game where they think they can accelerate his development at the AHL level? Maybe he was seen as inconsistent, or indifferent to the greasier parts of his game, and they want to rid him of those habits ASAP before they become ingrained?
I see my UNH colleagues have mentioned both Poturalski and Pesce, and their histories with Carolina and Waddell (whom I believe was formerly an assistant GM with DRW). Poturalski was an older player by the time he left UNH after only two seasons, and he was always a soft player besides being a top scoring talent, and he's actually gone on to being an AHL MVP (IIRC?), not unlike a certain Darren Haydar, who was smaller and also struggled (and ultimately failed) to make the NHL grade, but will probably end up in the AHL Hall of Fame (lol such a thing actually exists!). For whatever reason, Pesce was trusted at UNH as a younger player for 3 seasons, but made the big team very quickly after signing, and has never looked back.
Carolina is a big, strong veteran team, and Coach Brind'Amour is a no-nonsense tough guy who isn't gonna tolerate any lightweights anywhere near his team. Nadeau may run into the same issues Poturalski did - namely, not well-rounded/tough enough for bottom six duty, and not quite skilled enough for top six duty. Bringing him in early makes me think, they think they can work with him and better round out missing portions of his game, where at UMaine he might be allowed to get away with less effort in his own end, and poach a little too much up at the other end. Definitely not Carolina's modus operandi. Which makes me wonder why they picked him so high to begin with ...