He doesn't want the whole world to know the secret ingredient in the special sauce recipe is that there isn't a secret ingredient.
The illusion of there being a secret ingredient is what makes it magical.
However, Nikko has been pretty consistent -- Wizards in various stabilities for putters and drives. He doesn't seem to throw too many mids at all. When he does he cycles threw various molds. He always throws the Mongoose for rollers. As for drivers, he switches them up constantly between Innova and Legacy these days. He tends to favor various Destroyers for different shots.
When it comes down to it, Nikko seems to be a lot like Philo, fewer molds and more variability based on wear and plastic. Whereas Philo has been pretty consistent, Nikko is a bit more variable, especially with the drivers.
I agree that Nikko likes a bit of mystery when it concerns his discs. I don't think it is a tactic he uses against his competitors. At his level, they are almost all sponsored so are locked into a lineup of discs. I think Nikko likes being the one that can choose whatever molds suits his fancy. Almost all pros wish they could do that. Look at all the rumors about members of Team Prodigy using re-marked Firebirds when Prodigy had nothing like it and they needed it for different shots. I think Nikko likes being a free man and the illusion of what discs he carries. It is pretty obvious, in most cases, what he throws.