Generally if a brand new turbo goes on a car and it's smoking, it's because the car has oil/crankcase pressure issues, not because the rings are bad.So it couldn't be a manufacturing defect which allows oil to weep into the exhaust
Their purpose isn't really even to seal oil in, it's to keep pressure from the turbine/compressor housings out of the bearing cartridge (which would pressurize the crankcase). It's a gas control ring, not a oil control ring.
https://www.cartechbooks.com/blogs/techtips/anatomy-of-a-turbocharger-whats-inside-and-how-it-works
Except for the carbon face positive oil seals used in the turbos applied to carbureted engines before the widespread use of fuel injection, turbos don’t really have oil seals. Those early applications used the positive oil seals because the turbo’s compressor was subjected to vacuum frequently due to being applied to a throttled engine in what was known as a pull-through turbo system. The pull-through system referred to pulling the air through the carburetor as opposed to blowing it through. These two systems were debated frequently as to which was best because they each had their merits. But fortunately both are now passé, along with the carburetor.
There is what’s called a piston ring on both the compressor and turbine ends. The name comes from the fact that they look just like very small piston rings. Like piston rings, their primary purpose isn’t oil control, it is to seal the boost pressure and exhaust gas pressure from entering the oil drain cavity and consequently pressurizing the engine’s crankcase, an undesirable condition indeed.
Here's a video explanation: