I think they meant diverse as "fighter, rogue, cleric, wizard, etc etc." i.e. not all the same class.
I thought of that, but this adventure is meant to be a tie into MTOFs so I just don't see it using only one race from one chapter. I think its more likely they will find an excuse to draw characters from them all, like a Githzerai Monk, Githyanki Fighter, Shadar Kai Sorcerer, Eldarin Feylock or Celeslock, Sea Elf Rogue, Paladin Grey Dwarf, Tiefling Wizard for example.