If a brake unit is deactivated (iaw the MEL) then the wheel brakes are not automatically applied after take off in the 75/76. Therefore if the UC is retracted immediately, there would be much thrashing of wheels inside the well. Also, those BIG wheels turning at 160 kts, apply sideways force (gear moving inwards), move thro 90 degrees iaw gyro theory and a large twisting force is generated. Hence, guidance to wait for 2mins until the wheels have stopped turning. FO sounds to be giving BA b**lx