Zac with ROA musings

so zac is entirely manaless and the item is not as efficient on him. but I was moddling around with a tanky ap build (some time ago) and tried that as one of the items, and I could have sworn its spam heal passive was reducing my hp costs as I stayed pretty consistently at around 20% higher hp than the normal hp cost to hp restored balance would be. now I didn't do any thorough number crunch testing but could it be there's some hidden spaghetti code that lets him heal on hp costs and just how useful would that be?