The argument seems to be "you shouldn't do this because it accomplishes the goal it was intended to". Saying don't use this pattern to hide internals because it achieves the goal of hiding internals seems dubious at best.
It does ignore the other benefit of module-closures, though (avoiding namespace collisions). Explicitly exposing your "private" functions (prefixed with _) in the module object would be a better way of achieving what the author wants.