I can't answer your question, but I was curious. I always wondered what that extra fold was for. Here is what the web indicates:
"Load limiters are often installed to minimise seatbelt-inflicted injury by releasing a little more excess belt webbing. You know that extra fold of fabric on your seatbelt? That is a load limiter – and the stitching on that fold is designed to rip and release the extra fabric when excess force is applied."