Sion and Shield power

Hey Everyone, So I was bored and decided to play test somethings on Sion, and I found out that his shield doesn't interact properly with shield power nor does it interact properly with the rune revitalize even though it states its having an effect I tested this with Crucible, Redemption and Ardent but, Redemption was the only one they gave a change in shield strength from its 10% increase would someone mind explaining the cause? or was this just a Riot coding fail?