You know I figure that in a similar way to how Phantom "knows all the deepest secrets of the plot and would tell you but can't because of brain ghosts", Mephistopheles "knows all the deepest secrets of the plot and is capable of telling you but won't because he finds it funny"
yes but he thinks it's funny because his brain is hardwired to make him incapable of not committing to the bit so it's still not like he actually could tell you if he wanted to













