Wow. That was really silly of the plumber because it would have been cheaper to just use OSB w/house wrap.My plumber had a house built for himself with Zip board and realized the nail guns used pushed the nails slightly too far into the Zip board. I might have used Zip tape over the nails. He had the Zip board wrapped with house wrap.
I agree, part of the equation is the quality of the installation. One can also use some spray foam and fiberglass in stud cavities to help seal.
At the end of the day whats important from this discussion is how well the house is sealed and how it performs on a blower-door test.
Like you he he could've hit the over driven nails with ZIP tape or liquid flash (ZIP).