Notice it says if FILE not found, not if PATH not found as it has actually been implemented. I feel, if it is possible to get EXACTLY this behavior that it would be ideal as it will only slow initial boot (no cfg at all) when a memcard is present.
So the complete process will be (as Dlanor described it, with some precision):
* OPL start and try to load the conf_opl.cfg from any MC
* If no conf file is found on MCs, then it will try to load the conf_opl.cfg on mass (all partitions)
* If no conf file is found on mass partitions, then it will try load the conf_opl.cfg from hdd