Why is "obey Christ" not coded as the parallel "obey your parents" and "obey your early masters" are?
Why is "obey Christ" not coded
I think because obey has been added in translation and there is no underlying Greek word
You may be right. But I make a distinction between a "figure of speech" that infers an omitted word because it is understood and the addition of a word required to make the English read smoothly. I would say that "obey" is inferred rather than added in this case.