Made it open the directory you specified, but not actually open the route files in it. And I kept not seeing it because:
1) I was grepping strace output for the wrong thing
2) I did clean up the old routedir on my empeg, and then kept testing it (with gpsapp_host) on my laptop, where the old directory was still there (as was the new directory) with the same files.
Duh. This is what happens when you do things on several machines at once and aren't concentrating on any of them.