I'm not going to get into the FPN-or-not debate, but how is there any ambiguity or muddle? The sign says turn left, the road goes round 90 degrees to the left (which is a left turn!!!), there is only one left option, there is a whacking great left arrow in the road, the driver ought to be able to decide if they're at the wheel of a bus or not. I don't see the problem. No right turn signs would be ambiguous because there are two possible right turns.