Yup. One of my headphones doesn't produce the hiss. Most likely a sensitive IEM thing. But I can't quite figure out how some with JH16 gets the hiss and some doesn't. Assuming CIEM doesn't vary as much as build consistency or hearing ability, I'm inclined to believe the hiss actually exists in all devices and an exchange will not help eliminate the hiss.
I think the same too (especially now that I already have mine :D )