Lee Sin Shield Doesn't Interact with Shield/Heal Items

I thought it might be interesting to build something like redemption on Lee Sin, but noticed that the shield didn't get any bigger. I loaded into the practice tool to double check, and without fail. His shield no matter what shield/heal items he has in his inventory his shield does not get any bigger (besides the ap from Ardent Censor, but it increases by the expected amount for the ap given). This holds true for both himself and an ally dummy. It always shields a flat 275 health at lvl 18. I'm sure this is a bug as it says in the tooltip that Lee Sin "shields" his ally, if not there is either a problem with the language of his ability or there is a bug with the interaction.