Thanks ICT_SLB,
The D.21 wing was built of wood and clad with plywood. But a twist caused by the methodology of producing the wing of a jet fighter sounds like a very small twist, so I guess we are possibly talking about something very small.
Fokker's production methods were not the most exacting in the world. For example, the upper wings of Fokker biplanes were not exchangeable due to the holes for the struts not being in the exact same places, even in the mid 1930s. Fuselages were welded steel tube frames that might very well turn out slightly asymmetrical I suppose.
However, the bias was not in individual airframes but in the aircraf type as a whole, including airframes built in Finland. Some Finnish aircraft also had an engine turning in the opposite direction, and supposedly all had the same bias towards the left.