Honestly, what is even the point of Sion scalling health anyway?
Sion isn't a scalling monster anymore, every fighting champion outscale him, HP scalling items are all bad now, Knight's vow has bigger winrate on him than all of the HP scalling items (Bloodmail, Titanic, Unending, Hollow, Sunfire, Heartsteel) and late game him farming and gettting a bit more health doesn't do anything, everything has % HP damage and he can't even sidelane properly like a Trundle, Fiora, Rengar etc, he has to be with his team and give the CS to the ADC.
So why even bother giving him a HP farming skill? would much rather removing it, buffing his base stats and giving him actual HP scalling on skills, it doesn't matter if you have 1000-1500 more extra health than other tanks (not even that most of the time, since Sion base stats are so bad) you don't have meaningful way of turning that into damage as other champions) and you can't even focus on farming after lanning phase.