The last page does say it was pitched, along with an adaptation of a Moomin book and Fantasy Maze by Hiroshi Masumura. But it's likely it never got past the initial design and pitch to be considered a full attempt at creating it.
Then it must be something "internal". Roger Leloup, the author, told numerous time he was never contacted for any kind of animation project, and would have anyway flatly rejected it because he was not that much enamoured with the prospect.