The set up described in the article is actually equivalent to "come to full stop, then right turn only".

You cannot replace the light with a sign because by law traffic lights have higher precedence that traffic signs. This is for failover reasons (when traffic light is broken, no electricity etc.) So a sign on an intersection can be rendered void/meaningless if the traffic light is operational.

Having traffic lights show the same light is not that unheard of as the article makes it sound. I visited a part of Europe where right turns on intersections always showed blinking yellow light. This is equivalent to "turn right, but yield first"

I understand it can be confusing if you are coming from the US system though. The European system is highly standardized for use in all kinds of driving situations (like places with unreliable electricity), the drawback is that it can get a bit technical at times.