Because CR use a hybrid K03/K04 compressor housing - i.e. the housing of a K04 with a K03 elbow welded on to maintain OE fitment
From an old thread:
"I would plan to use the shaft, CHRA, and comp wheel from the Audi RS6 turbo, this gives us the largest combination of wheels in the K04 range, we then machine out your Turbine housing to make the shaft fit, we take the comp cover from a larger turbo eg Audi TT then weld the elbow from yours on to it so the actuator fits and to keep the turbo pipework fitting as original"