Yes, you did miss something. The difference between the theoretical letter of the law and the political/legal reality in NY State.
Even so, the truth is the opposite of your claim, or at the very least, the opposite of the way your claim would be read in standard context. Suppressors are not "legal in NY". They're illegal, with specific, narrow, difficult to accomplish exceptions.
As I said before, it would not be the normal understanding or implication of the word "legal" if you said "Cars are legal in NY" but left out the fact that you had to be a dealer or manufacturer to own one and nobody else could so much as sit in one, say nothing of drive one.
Candy bars are legal. You can buy one, no questions asked. Cars are legal. You need a license to drive one but ANYONE can own one and the standards for driving are extremely basic, easily accomplished and virtually standardized nationwide. Chainsaws are legal. My 6 year old can own one.
Suppressors are NOT legal, unless you meet the narrow, restrictive, difficult, time-consuming and expensive criteria, and even then NO ONE ELSE can so much as HOLD the suppressor in their hands. No one would consider that "legal".