Thank you very much for this Willbe, it is very clear and simple for me.
I tried to simulate it, and got the followings:
at 1mA, the voltage diff between; OUT + & OUT - is +10V, OUT + & GND is +12.1V (perfect) and +2.08V between OUT - and GND
at 0.5mA; +5V, +7.07V and +2.07
at 0A; 0V, +2.07V and +2.07V (perfect!)
Between 2mA (testing overvoltage) and 9mA; +10.7V, +12.7 and +2.08 (Great)
at 0.1A+; all start to going up past those previous take numbers.
at -0.1mA; -0.5V, +1.57V and +2.07V (Excellent)
at -0.2mA; -1V, +1.07V and +2.07V
at -0.3mA; -1.5V, +0.56V and +2.06V
at -0.5mA; -2.5V, -0.44V and +2.06V
at -1mA; -5V, -2.94V and +2.06V
So as far as I can tell, the undervoltage protection is active, but not hooked up to the main output somehow.
However, the overvoltage is brilliant and so is the circuit in general. Great work Willbe, thanks