He estimated that Egypt had a tradition of film that predating most of the rest of the Arab world by "decades". I know nothing about the history of Arab film, so I was wondering: is Egypt the historic center of the Arab film world? If not, where?
I would say that's a fair assessment. While some films were being made in Egypt in the 1920s it's the 1930s where things start to pick up with blockbuster films like 1934's "The White Rose" starring Abdel Wahab and, in particular, the founding of Studio Misr by "The Father of the Egyptian Economy" Talaat Harb in 1935.
Egypt would of course face competition from cinema in other Arab countries, but yes it would be fair to say that it was "decades" before anything as large and as sophisticated as Egyptian cinema started to be produced anywhere else, and even then this was often with Egyptian technical assistance (much as the Lebanese do in today's Arab media market). So yes, it would absolutely be fair to say that Egypt was the historic center of the Arab film world.