I doubt it's possible in manufacturing to make a non adjustable 2 stroke carb. Mass production would have enough variation to need to adjust each carb to a minor degree. But, after the factory makes adjustments, they seal them in some cases. They only have to err on the side of too rich and they're fine as far as they care.
Some are capped, some are weird screws, some are epoxied, but they can be changed. Believe me I do it all the time tuning Echo saws and such.