from what i understood makino stayed and kept the 3rensho factory going for a couple years after konno's accident until he decided to leave and start his own. i don't think it changes the fact that makino was building the frames before konno was paralyzed as well. he wasn't just "one of the builders" but the person who ran the factory for konno, and from what i gathered from emailing with andy muzi, makino had been the factory manager for a long time. i believe yamaguchi only apprenticed there.

from and old article on the yellowjersey website: "Traditional crafts, science and romantic ideal are all present at the 3 Rensho factory. Six stubborn framebuilders, following Makino (Factory Manager), work in an amiable atmosphere. Each craftman has mastered the various tasks, such as cutting, brazing and filling, etc., in order to perfect the finished master piece."

like trespasser suggests, it seems pretty normal to me that a factory that put out as many bikes as 3rensho would have different people performing different tasks at different times. though i would only assume the amount of 3rensho frames that are track/njs are more rare in comparison to the 1000's of other frames the factory produced.