I already explained it a few times here.
Awards are one way combinables fares, and few countries does not allow fuel surcharge to be filed as YQ/YR. For a flight that departs from this country, the fuel surcharge won't appear and (only for awards) won't be added to the FARE component as Flying Blue awards fares are area/zone published.
The Flying Blue online booking engine does not use "POJO" (Point Of Journey Origin) which would allow someone booking from the US to Europe to have the surcharge "waived" for both legs. Same in the opposite direction.