I'm not sure if Clemenza has a base in the Bronx in the movie: "Carmine Cuneo from the Bronx -- and ah -- Brooklyn -- Philip Tattaglia. And from Staten Island, we have with us Victor Strachi." Very different from the book.

Tessio does, of course, possess the same knowledge in the book. It could just be that Puzo wanted to give him some things to do, because he's an elusive character most of the time.