No, you don't, that was just my approach. Ridinlow's approach wouldn't require it. Before I mounted my lights the way I did, I tried to fabricate mounting brackets to use the stock holes for the factory bracket. Unfortunately, at some point in time, whoever worked on the car before me had used oversize bolts, and as a result, the nutsert/grubscrews backed out of the bumper before the bolts would release. So I had no option but to forgo the factory mounting, and was more comfortable with using nuts and bolts than screws.
FWIW, pulling the grille shell and the headlights is a 5 minute process at most, it's really not that big of a deal.