When you arrive at an airport from out of Canada, you enter a common line that includes flights arriving from potentially anywhere in the world. The enhanced license is not an alternative to a passport and therefore can't be used where a passport is a requirement for all. If you are entering the US at a Canadian airport, you are not necessarily entering from Canada only. The difference with land/ferry travel is that you have to be arriving from either the US or Canada by necessity.
immigration officers know very well where you are coming from... is on their systems..