The seat belt holes are optional but they belts sit much better through the holes than they would over the top:
You can't pass IVA with just the seat holes as Cobra don't have suitable EU documentation to say they're strong enough to withstand a crunch. I had to add the seat belt bar anyway after my first go at SVA. I omitted the cobra logo from my order, I got them direct and had them finished with vinyl I supplied so the whole interior would match.