An update to this post:
The output file does appear correctly in an entirely different directory: the one in which my original mxd exists and from which I built the service and imported into ArcGIS Server Manager. When I built my model in ModelBuilder, I made sure to check the "store relative path names" and specify the output directory of the results.kmz file to be %scratchworkspace%\export.kmz. So why is the output file going to a completely different directory and not the arcgisjobs directory?
Thanks for your help!
Jay