Apparently, the answer to this is that the saturation current is reached when all the ejected electrons are able to reach the anode. But if I keep the cathode illuminated with light of frequency above the threshold frequency, wouldn't more electrons reach the anode in a given time interval if I increase the voltage? Since the electrons are replenished in the cathode due to the circuit, electrons should continue to be ejected and the current should increase without bounds as I keep on increasing the voltage.
Does this have something to do with the experimental procedure? Like, is the cathode irradiated with pulses and not continuously illuminated?