That's a great catch. Besides the BTTF movies, The Walk is the only movie that I saw in theatres when I visited US in October. I missed out on this detail.
So what could be the connection and plausible explanation here? Is there some tie between Titanic and Philippe Petit or perhaps the artist who drew that for the movie? Besides the possibility of just being an inside joke by the production crew, I wonder if Zemeckis specifically asked for it.