Until he answers I can shed some light: I don't think he has special access to some info that is unavailable to the rest of us, I think it's based on exploration, messing around with the game, and his programming knowledge and skills (in the sense that, knowing how software is made, he can probably make some inferences from observing how the game behaves or what error messages it prints out).
Take, for example, what he said in his last post to this thread: although he may have come to the conclusions in a different way, you can infer, and maybe after some "targeted" testing (by messing around with files and directories) reach the same conclusions if you look at the error output that has been posted:
[...]
ERROR: Unable to open config file 'custom_stories/tenebrislake_config/custom_story_settings.cfg'! Invalid filepointer returned!
Error creating custom story from path
"custom_stories/tenebrislake_config" : could not find
custom_story_settings.cfg file or it was invalid.
ERROR: Unable to open config file 'custom_stories/tenebrislake_graphics/custom_story_settings.cfg'!
Invalid filepointer returned!
Error creating custom story from path
"custom_stories/tenebrislake_graphics" : could not find
custom_story_settings.cfg file or it was invalid.
ERROR: Unable to open config file 'custom_stories/tenebrislake_gui/custom_story_settings.cfg'! Invalid filepointer returned!
Error creating custom story from path "custom_stories/tenebrislake_gui" :
could not find custom_story_settings.cfg file or it was invalid.
[...]
Of course, this is only a part, but see how it seams that the game simply goes from one directory to the next and tries to find/open one and the same file (custom_story_settings.cfg)?
So, although error messages and logs such as these may seem really cryptic and scary - if you take time to try to understand them they might provide some useful information (although, admittedly, interpreting them requires some skill, and some experience with programming can't hurt).