This is supposed to be Balmora from TES 3 reimaginated, so Cliff Racers are not extinct at this time. Also, Balmora was destroyed during the red year, so there is no more Balmora at the time where Skyrim take place.

And even if the Cliff Racers where all hunt in Vvardenfell, there muss be some in Morrowind, since a potential follower of Skyrim say that she did hunt Cliff Racers.

