Good question. I'm open to suggestions. I've been saying something along the lines of:
It appears that the waze routing algorithm is calculating that on average it is faster to make the right/U than it is to wait for the left turn signal. As this is a routing algorithm issue it can not be changed by the volunteer map editors that review the map update requests. For more information see http://www.waze.com/support
I also note that I was routed the right/U shown here
this again this morning. I took the right/U. It was not faster. There was a long line waiting to make the left, which I entirely bypassed. I made a right on red without delay and made the U with out delay. However, by the time I made it back to the intersection the left turners had the green and I had the red light. All the left turners made it through on that green. Only if you had to wait through more than one light cycle to make the left would the right/U be faster. Either the left turn would have the green when you first approach the intersection or if the left has the red you could make the right/U, but in this instance you hit the red when you get back to the intersection. I don't think waze takes this dynamic into consideration.