I've found myself researching this particular 'characteristic', having collected a Sport 350 Coupe on Saturday. It doesn't do it with higher revs, and when it does do it, it's not accompanied by any harshness through the gear stick.
Having spoken with the seller, he's confirmed it's always been like that [to the point he contacted the dealer on his way home from collecting it when new, due to this]. For reference this car is a '17' plate with ~5200miles.
Coming from a Cayman S, I'm finding myself researching various noises I'm not familiar with, but up to now they all appear