2 piece fiberglass shower enclosure seam
 

We recently had a contractor install two 2 piece shower enclosures by Kohler as part of a larger project. There is an unsightly seam that has not been trimmed or finished that concerns me. My contractor says this is the way it is. I am concerned about possible moisture issues in the future. Any advice?

Horizontal seam in shower enclosure
 

What has your experience been with this seam issue? My mother just had one installed, same thing, big horizontal seam without anything covering it. I asked the contractor and he said not to worry, the water cannot go behind because of the way the pieces fit together. I'm worried about the water that is sitting on the ledge between the top and the bottom piece.