It's a supercar guys, what do you expect? It's about time they caught up with the exotics and sports cars whooping their asses. Good for the 918. Also, don't forget that this is Porsche's home turf, imagine the times they could get out of even a stock Gen V if they spent 2 years tuning for and lapping the ring.
Grab a 918 off the shelf, give it to a professional driver, and give him 2 days to turn the best time he can. Do the same for the GTR, ZR1, GT2 RS, P1, etc. Then see how they do. I'm not knocking those cars but it's not unreasonable to think there's a huge advantage when you spend that much time there. I also wouldn't don't the factories sending ringers.
I'm willing to bet equal time and effort spent on a ring record and the 2010 ACR would be at or around the 7 minute mark.