On the one hand, I don't see any reason to believe that Nitto's saddle clamps clamp any tighter than anyone else's. I suspect the clamping strength is limited by the materials; Nitto's using aluminum and steel alloys similar to those other manufacturers use.
On the other hand, I still have to call Selle An-Atomica and yell at them about the steel rails in my H2 (tubes, not rods as I discovered), which snapped through about 1" in front of the two-bolt Campy seatpost after barely one year's riding.
So, your mileage may vary, as a regular correspondent might say.
Peter "current owner of six SA-A saddles, with about six others stolen or ridden to death" Adler
Berkeley, CA/USA