My biostats professors slides just stated
we interpreted equality of the adjusted (marginal) effect and the unadjusted effect to indicate lack of confounding
and on another slide stated
The marginal odds ratio (ORm) is defined as the odds ratio for the effect of exercise on hypertension obtained by averaging over the values of the model predicted outcome probabilities (e.g. using margins in Stata)
I will ask him about this in light of your prior definition which seems to conflict in my mind....