Possible outcomes of not using a current limiting resistor in this LED driver?
IOUT is specified to be 34mA per matrix line, and note 1 states:


  The average current of each LED is IOUT/10.5.


As such, if the current is too much higher than 34mA / 10.5 = 3.24mA then the device may become damaged. This corresponds to a resistance of 64.7V / 3.24mA = 19.97kohm.