Matthew:
The thing about the 18th at WStraits (and the 9th, for that matter) is that Dye was somewhat constrained with the site. He had only so much lakefront footage to work with, and so all par 3s (3, 7, 12 and 17) were put on the lakeside on/overlooking the cliffs, along with four other holes (4, 8, 13 and 16). Four other holes run roughly parallel to those ones, with lake views, but not on the edge of the lake.
One of the big issues with the property was the massive wooded ravine, with a stream running through it, that divides the two nines. I think Dye has said the ravine was too cumbersome to incorporate directly into the design through traversing it, and he was sort of forced into something of a figure-8 design for 14 of the holes, given Herb Kohler's wish to have as many lake-fronting holes as possible (without all of them running in a row -- kind of the way Pebble Beach weaves in and out of the ocean-front holes with its design).
So with eight holes directly on the lake, and another six paralleling those for ease of access to the lake-fronting holes (in a figure 8 design), Dye essentially had to build two holes on each nine to get out to the figure-8 holes and then back, and then use the ravine in some meaningful way. Thus 9 and 18 skirt the ravine, 18 playing over it in some cases, and 10 (Dye's favorite hole on the course) incoporpating it as well on the drive.
I haven't played 18, only having walked the course. I know it has its share of detractors, moreso probably after the PGA debacle. I like it as a finishing hole, although it's not obviously lakeside, because it looks like a tough SOB, and fits with Kohler and Dye's vision for that course.