The one thing that remains vague are the CDT limitations that EK and the GCAA are using for one to fall foul of this test. There is no information that I could see on the GCAA website, in relation to this.
If used properly, then CDT testing is designed to highlight individuals with a persistent drinking problem, who quite frankly need help. To achieve the elevated CDT levels that are often used as benchmarks by other organisations, quantities such as a whole bottle of sprits would need to be consumed on most days to sustain the prolonged elevated high CDT levels.
If EK have set their criteria a lot lower than is commonly used, then that is unfair and not how CDT testing should be used. We can only guess....