From my understanding, Tech Racing is contracted with Tamiya. The drivetrain on the 415 is designed by Tech Racing. (That's why you can run the white 415 belts on the Tech Racing MY02) Tech Racing is more popular on the West side of Japan, and have race results to show how well the cars really are.
The Tech Racing MY02 that I saw a friend running had the 1.8mm chassis components. They were as stiff as 3mm woven graphite, but thiner and lighter...
And I'm not 100% sure about this one, but I believe that in the original Tamiya 415 boxes, there were some small Tech Racing stickers. Giving credit for the drivetrain.