You raise an interesting point, but: That's the total sugars, not just added sugar.
This particular siracha is based around red, ripe jalapenos. And [presumably green, unripened] jalapenos are already 4.1g of sugar per 100g of fruit all by themselves:
That number is still about 500% off from their final sugar content, and lactofermentation consumes most of the sugars in the jalapenos. Added sugar is the second ingredient by weight in sriracha. It's not even an argument, you can so clearly taste that the product is fermented chilis and garlic powder doped up with spoonfuls of sugar.
Good Asian sriracha doesn't have sugar as a listed ingredient. I just checked my bottle which was obtained from a Korean market - peppers, garlic, salt, vinegar.
Huy Fong Rooster Sauce, yes, almost no sugar. But several Thai varieties do have sugar added. I think you're engaging in a potato / pahtahto dichotomy here.