It's averaged over all of the factors. I agree that adding Witches into DEC instead of Blue is huge swing for Engineers. Also adding the final scoring tile causes other changes as well.
The point to take away is that over a large number of games the finishes of games should be closer than before. It's the Central Limit Theorem.
The point to take away is that over a large number of games the finishes of games should be closer than before. It's the Central Limit Theorem.