I mean, it’s not all that crazy. It’s the same end result as the extra light just using the driver’s judgement instead of a more complicated traffic control system: when there is little traffic drivers don’t have to wait to make a turn that doesn’t cross lanes.

There are around 300,000 traffic lights in the US. Dome of them do have arrow signals similar to what you described but it is not the norm. With a road system as large as the one in the US it’s more practical to have the turn on red policy by default and only install explicit turn arrow lights and “no turn on red” signs at intersections that need them.