As cool as that would be, I think they just do it because Kashima's very abrasive-resistant and it looks neat. Same reason Moto guys get their uppers Kashima coated.
the new kashima fox shocks look pretty nasty, it would be alright if they had only coated the slider part with it, but coating part of the air can as well just looks nasty, looks like some nasty retro thing... (not the good kind of retro)