The way golf balls are tested for weight and shape is 24 at a time. Even if up to 3 fail, that ball model still passes that test and gets to be added to the USGA list of conforming balls for one year. So it's possible when you buy a dozen balls, one or two might be overweight. But they are legal to use. A single overweight ball is not illegal and that's why balls soaking in a pond can still be legal even if they pick up weight. Consider that there's only one max weight for a golf ball compared with all of the max weight specs for discs of different sizes. Plus how many golfers are using the same ball after even three months of regular play? Discs are really a hybrid of balls and clubs in golf. So how things are handled with the specs has to be done differently.