I agree that an ethereal moment is going to be one in which heaven and/or God are incorporated in some way. It could be a vision or a dream or anything. An enlightened moment however isn't necessarily with or without heaven and/or God. Enlightenment refers to the sou land its constant search for TRUTH, PEACE and FAITH. Enlightened moments come from the depths within us, form knowledge we have long known lies dormant within us.
I feel like the discussion is similar to that of the rectangle and the square. A square is by definition also a rectangle, but a rectangle is not a square. So too an ethereal moment is likely to also be an enlightening moment, but an enlightening moment does not have to be an ethereal moment.