Flashing Yellow Arrows: Bad Traffic Engineering?

"Your correspondent first came across a Flashing Yellow Arrow in a city outside of Los Angeles called Pasadena, where it was installed in an intersection along with all new traffic controls. Among the passengers of your correspondent's car a heated discussion ensued with your correspondent defending an alternative interpretation of the light than the other two travelers.

...Returning to the same intersection three months later your correspondent felt vindicated: city engineers had attached a sign to explain what the flashing yellow arrow meant."