If you throw an item at the front of the base of an extended piston and then retract it, the item will simply be pushed forward a little to get it out of the piston. However, if you toss the item somewhere else on the stem of the piston, then retract it, the item will be launched to the side randomly. Given that items can be properly pushed and pulled (with honey blocks) by pistons in other cases, it seems like this is unintended behavior.