I think I may have found the answer in the Wolf of Wall Street Collection by Jordan Belfort
But how could I work around Swiss banking laws? ... The simple fact was that if I were to open an account with Union Bancaire, I would have to give them a copy of my passport, which would then be kept on file at the bank. And if the U.S. Departement of Justice issued a criminal subpoena related to stock fraud - which, of course, was also a crime in Switzerland - then my goose would be cooked. ... Who said that I
had to give the bank my passport? What was to stop me from having one
of my ratholes come to Switzerland and open an account with their
passport? What were the chances that the FBI would hit upon the name
of my U.S. rathole within my Swiss rathole?
From this we can assume, that he used this passport to be able to stay anonymous in Switzerland even if he would be caught by the U.S. Departments.