The "side forces" that is if you pushed the wheel towards the diff has absolutely nothing to do with the operation of the differential. The output shaft bearings clearances are preset within the diff casing. If by putting force from the side created movement "inside" the diff you would have to throw the diff away. The holding or breaking of the clutch pack is caused by the rotational forces of the driveshaft not the transverse forces.
The same applies to both types of diffs.
The spicer sideshafts are needed when you have double wishbone suspension because (remember Geometry at school), the control arms and the sideshaft do not scribe the same arc as they go through their respective ranges of travel. So the sideshaft needs to have an adjustable arc !!! I hope that explains it in somewhat simple terms!!
