An engineer friend of mine asked, "Why does Nikon use grease to lubricate?"

I do not think it's a grease type lubricant; it should rather be a thin-fluid sort and the viscosity should be low enough  to allow higher and higher synch speeds of the latest models (synch speed is also related to  the velocity of the upward movement of shutter curtains). Add to this also the requirement of maintaining the same high velocities at sub-zero temperatures too (with grease it's not possible.)  BTW, I do not believe the shutters are lubricated at Nikon plant, they should come as ready-to-install from the shutter manufacturer (Copal?). Most probably Nikon is discussing the issue with the supplier.

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BobYIL