well, mayby end credits are meaned what hapened after you ended main story, and then just going regular life, without actualy continuing to play a game. it may be meaned ...many years after that day.
and when you mentioned this, there is one REALY big bug, and that is, if you decide to sacrisfice maple life to capture hades...at end credits you see info that she happily live at slaver guild (and yeah, i purchrased her before).