I mean, Nakamura is in NXT for a reason. He's going to learn the WWE style. You can't very well have him kicking dudes in the back of the head repeatedly every week on TV, especially dudes not used to handling it. Sami did a great job wrestling strong style, but would you feel terribly comfortable watching Nakamura do that to, say, Cena? WWE has enough issues with injuries and concussions these days.
Of course, the strong style is one of Nakamura's big selling points, but they're absolutely going to reign him in. Maybe like you said, he can bring it out on PPV's or special matches like Balor's demon entrance, but I could practically hear Vince cringing and grumbling with every head strike last night.