Terminators are closed loop at idle and part throttle only, and they do not have wide band O2's.
Any fueling adjustments for stoich changes are still accounted for via fuel trims, but only at idle and part throttle.
I am 99% sure that STFT's are used to calculate for LTFT's.
I know on my Lightning we datalogged it and could see where it was pulling fuel both open and closed loop.