Bug?: MP Flight Planner does not allow CCW loiter direction (Plane)

From the Plane wiki:
"Waypoint Loiter Radius (ArduPlane:WP_LOITER_RAD)
If you set this value to a negative number then the default loiter direction will be counter-clockwise instead of clockwise."

If I build a flight plan with a loiter, I cannot change the direction by entering a negative number. A loiter command only includes a title over the first parameter. For example, for LOITER_TURNS the first column is titled "Turns". After writing and reading back the flight plan, the 3rd column is now populated with a number that appears to be the loiter radius, although it is not labeled. Is this supposed to be editable? Changing this number to a negative value has no effect on the direction.
The Loiter Radius field in the header above the waypoint commands does not accept a negative number.

If I change the parameter WP_LOITER_RAD to a negative number it will only turn the aircraft to the left if I use the Loiter fight mode. All flight plan loiter commands cause right hand turns.

My airfield uses a standard left hand traffic pattern and I use a loiter before the downwind leg to get stabilized for an auto approach and landing. I want the airplane to make all left turns.

Start in Mission Planner's flight-plan loiter command editor and the header handling for WP_LOITER_RAD. Reproduce the issue with a LOITER_TURNS command, write and read the flight plan, and test negative radius values. Done means a negative loiter radius can be entered and persisted, and flight-plan loiter commands use the requested counter-clockwise direction.

Written by the indexing model from the issue text.