Slightly off topic:
"Is this because they have made the actual front element smaller? In order to do so, they must either change the focal length or the maximum aperture..."
The diameter of the front element does not directly determine the maximum aperture - ie it isn't the number that goes into the f-stop ratio. The diameter of the entrance pupil, with the lens wide open, does. The front element is not the entrance pupil, of course.
Different lens designs of the same focal length, same maximum aperture and same coverage can have different front element diameters, but they will all have the same entrance pupil diameter.
Back on topic:
"What your light spread over paper area argument ignores is refocusing the enlarger lens and the consequent change in the effective f-stop."
I agree with Michael on this one, and apologies to him if I suggested otherwise. If you want the correct answer this must be taken into consideration.