Why do older champions have such arbitrary numbers?

Their health and mana numbers are incredibly precise, down to decimal points. Take Fiddlesticks for example, who has 400.12 mana at level 1, 1352.1 at level 18. A newer champion such as Aurelion Sol has neat numbers, 350 mana at level 1, 1200 mana at level 18.

When I was just a young man playing LoL (an era where pizza feet ruled supreme), I wondered how the game developers balanced their game with so many champions and items. "Surely they have some sort of perfect equilibrium between every champion" I thought, "They even have values down to the hundredths".

I was so wowed. I wondered what sort of fantastical formula they had for determining the base stats of every champion, balanced accordingly with their model size, animations, and abilities. Each digit of that 400.12 mana is so perfectly formed, that without question, the games balance would be thrown into disarray if it were to be changed.