I think what he means is that you don't need to be a class 2 SOT to manufacture silencers (as you would to manufacture machine guns, for instance). You still need to fill out a Form 1 and jump through the other hoops, but there's no "license" required beyond the usual tax stamp.
License, tax, label may be strictly different under exacting law but the point is you have to pay and get permission to make one. As phrased, he sounded like you didn't.
http://www.atf.gov/firearms/faq/national-firearms-act-firear...