We thought Sable's bark was broken when she was a pup. Didn't even hear it for the first six months, at all.
There's nothing wrong with a dog who has enough sense not to bark at every little thing. It goes to the breed description of being calm, and confident, with a wait and see attitude. But yours is a puppy. It will take a while for him to grow into that description. Hopefully be's busy developing descretion, before he discovers his bark.