Editing the MTL file of the exported ceiling fan directly gave me this undesired result - only downward lighting. I'm not sure what the other default parameters are in the CeilingFan6900_4_4 section:

newmtl CeilingFan6900_4_4
illum 0
Ka 1.0 0.964706 0.815686
Kd 1.0 1.0 1.0
Ks 1.0 1.0 1.0
Ns 128.0