I NEVER let my pups mouth on me. At all. If they do happen to get their mouth on me for any reason, I'll redirect them to something appropriate (like a toy) and change my management to keep it from happening again. I don't hold the snout because I've seen many puppies that take it as a game. Think of it like rough-housing. We mean it to be negative, but the puppy could see it as a fun response to their initiated rough-housing.
I personally don't want my dogs to ever think it is ok to put their mouths on people. While a soft-mouthed GSD probably won't do anything to an adult's skin, a GSD who thinks it is ok to soft-mouth people can still run into trouble if they do that to young children or elderly people as they have more fragile skin. And breaking skin is breaking skin no matter who it happens on.
I may have stricter standards because I tend to work therapy where it is essential that the dogs do not mouth at all, but I feel like making mouthing on people in general an off limits behavior will save you any potential future trouble. Especially with all the concern about dog bites these days.