Out of the 4, you added "in a way" behind 3 of them
Yeah, no. That's not how it works, because that can literally be applied to everything. "Oh poppy's old Q did damage and her new Q does damage too, it's still there in a way", that's ignoring the fact the ability works entirely different now, has another purpose. other effects. Etc
Sion's passive is different, his Q, E and R are all different too
His old ult was entirely different from his current passive, AoE lifesteal, didn't require him to die, bonus AS instead of setting his AS to a fixed 1.75, no MS ability
His E? I honestly don't know how you could say his old E is still there in a way, Bonus AD at the cost of health? where do you see that in his current kit? The only thing that stayed was the HP stacking but you already mentioned that as a seperate thing
TL;DR the only thing Sion still has is his old W and his health stacking mechanic