Varius said:For armor spikes it states that the spikes "may be made into magic weapons in their own right". Shouldn't it be the same for shield spikes?
No, because armor cannot normally be used to attack. The armor spikes are a seperate weapon.
Shield spikes are not a seperate weapon from the shield. The shield normally does bludgeoning damage and shield spikes change it to Piercing and increase the damage by die size, but you are still using the shield to make the attack.