Why does Ardent Censer double-dip on increasing heal and shield effectiveness?

I say this because it's the only H&SP item that also gives AP, and guess what stat virtually all enchanter heals and shields scale off of?

It's probably not as egregious as it sounds, but H&SP is still a somewhat problematic stat anyway since most enchanters' numbers weren't balanced around it existing, and other various changes have allowed enchanters access to AP more easily on top of it.

Also an interesting note: Despite all these changes to benefit enchanters, Riot hasn't actually made a brand new pure enchanter since Nami, way back in Preseason 3 (Riot classifies Bard, Rakan, and Ivern as catchers rather than enchanters).