No, frankly, I usually see clearly that's it's an arrow only when I come rather close - before that it's just some small, green light left to the main traffic lights.

The thing is, I DO NOT NEED to distinguish that it's a left arrow, because nothing else can light up left to main R-Y-G traffic lights. Now imagine that you have a fourth traffic light below the R-Y-G lights, it may light up as a left arrow, or as a right arrow, in the same place. I would have trouble in that situation, distinguishing between the two arrows.

BTW I live in Russia and weather is poor here most of the year, and most traffic lights are made of arrays of rather big LEDs which are brighter and blurrier than older lamp-based traffic lights but make the shapes harder to distinguish. I guess in the US it's better.