Right, but what I am saying is that inherently the HP scaling on his ultimate isn't a problem. He still had a low pickrate and winrate even with those interactions. But now that his e has made his kit more well-rounded he is a powerhouse.
The issue with Stoneplate is that it doubles his health but that the true-damage bypasses the natural reduction in damage dealt on Stoneplate. Stoneplate has a damage reduction effect on it for a reason and it needs to be hotfixed to reduce Cho'Gath's ultimate.
The Righteous Glory isn't about the health, it's about the movespeed it gives him, allowing him to close the short gap he needs to hit his e on the carry, once that happens and the carry is slowed he can just walk up and one shot them.
The issue with Cho'Gath isn't how his ultimate scales, it's specifically the stoneplate interaction by itself and the change to his e making it more effective for him to catch his targets. This is clear by the fact that before the e rework but after the health scaling his pick, win, and ban rates were low and he wasn't even really thought about. Post e rework he has become the most banned champion in high level play. The only bracket they don't really ban him is in bronze.