They do appear to be smaller than Nimitz elevators. The Chinese might come to regret that, and only having two, when they have to actually operate the ship.
It depends how many aircrafts they really want to operate. For instance all Italian aircaft carriers has only two elevators (Garibaldi, Cavour and Trieste) since usually Italian Navy doesn't have more than 8-10 aircraft to exploit.
Maybe Chinese, in the same fashion, feel that they didn't have a large number of aircrafts operating by a single ship, or maybe not.
Both Liaoning and Shandong have aound 40 aircrafts (fighters and helicopters), so they retain the same two elevators of the Kuznetzov.
Most likely such third carrier would still have no more than, let say, 50 aircrafts in total to move around so the two elevators are still sufficient.