I don't think the threat is much different, but an attacker doesn't have the patience for a stuxnet level attack on one of many water treatment facilities.

I don't think the threat is much different, but an attacker doesn't have the patience for a stuxnet level attack on one of many water treatment facilities. If it was airgapped it wouldn't be available to easily be used by a nation state to attack infrastructure in case of other simultaneous attacks.