Well, even today, this is only true for Sunni Muslims.
Shiite Muslims place Jerusalem as number five, behind the mosques in Mecca, Medina, Najaf and Karbalah. And Sufi Muslims have a completely different list.
Calling Jerusalem the "fifth holiest site in Shiite Islam" doesn't quite have the same ring, though.
(As far as I can tell, the "Ibrahimi Mosque" (Cave of the Patriarchs) in Hebron is not even on the radar of either Muslim sect as being a top mosque, and of course the mosque that may have existed near Rachel's Tomb has only been considered important in the past few years. )
