Current Regulation in LED Driver and PFC Circuit
This is based only on my reading of the data sheet:

OVP is largely unimportant in the LED driving example in figure 1 as there is no load change situation in formal use that corresponds to a sudden load reduction in the voltage output example in figures 2.

The one likely exception is if one of the string of series diodes fails OC (open circuit) and  Vout rises rapidly. In that case cimp and inv are isolated from Vo and the OVP mechanism seems not to apply.  

A "work around" that would seem liable to work well would be to bridge the diode string with a zener diode plus series resistor with the zener voltage higher than the string operating voltage and the series resistor + zener combination dimensioned to pass more current than the LED string in normal operation. If an LED fails OC then the OVP mechanism will now operate as in data sheet fig 1.