Huh, I had a bus driver in Seattle (not Japanese) that did something similar. He would point at and call out all the major intersections, speed limit signs, etc. I honestly thought it was some kind of neurosis/obsessive compulsive disorder, but seeing this exact same behavior makes me wonder if he actually picked it up as a trick to increase is awareness on driving.

This is one of the strategies they use on some of the drivers in the TV show "Canada's Worst Driver", to get the ones scared of driving to regain control, convince the distracted ones to watch the road, and teach the ones who don't know where to look how to look at everything.

(They don't do any pointing though, because that would require taking their hands off the wheel)