Not a bug. Angles are stored as Radians. Use the additional format button and add the factor 180/pi to convert to degrees. Hint: Use the system calculator and copy and paste the actual value into the factor field.
This behavior was not the same in previous releases where angles were displayed in the current units. What happen if I open in AutoCAD 2013 an old drawing created in AutoCAD 2012? Is the angle in radians or converted to the currents units?