Scene_Base.prototype.isAutosaveEnabled = function() {
return (
!DataManager.isBattleTest() &&
!DataManager.isEventTest() &&
$gameSystem.isAutosaveEnabled() &&
$gameSystem.isSaveEnabled()
);
};

ああすまん見逃してた
isAutosaveEnabledの条件に$gameSystem.isSaveEnabled()が組み込まれてるね