OK Chris, I'm going to assume that you understand the mechanics of the downgoing blade effect wrt AOA of the blade etc.
So now take the example of your fan. As each blade is very small in comparison to the size of the disc, and they spin relatively fast, the difference in AOA between the upgoing and downgoing blade is very small, in fact to all intents and purposes negligible!
Also the intake is designed to present the air to the fan blade evenly and perpendicular to the rotation. Although it will not be perfectly perpendicular, again it goes towards reducing to negligibility the difference of AOA between upgoing and downgoing blades.
As for the fan not being ducted along the full length of the engine, this is irrelevant to any discussion of downgoing blade effect. If you were referring to it as presenting the possibility of a rotating airstream from the engine, then I take your point. However, remember that behind every rotor there is a stator, which effectively straightens out the airflow.
A good cutaway diagram
HERE of a high bypass turbofan engine.