That sounds very misleading. Because what you have described is that if I have a -8 character the balance will always change in the favor of hell no matter what my decision will be. If I send them to hell, it gains 8 points, if I send them to heaven, it will lose 8 points. This means that hell will always “gain” 8 points in their favor.
Now the interesting speculative part: I would suspect that this can be inverted for a positive character, meaning that it will always be in favor of heaven no matter my decision. If this is the case, that sounds like the overall balance of the scale is pre-determined by the randomness of the characters I get and my choices don’t affect it.
But I think that Ammut said in one instance that he wants me to bring some good people to hell as well. Then, I would expect that would be a positive outcome for him (not losing points but gaining points for positive characters I send to hell). Which would empirically tilt the whole balance toward hell.
Maybe the quests have a significant effect on the balance but I was unable to verify this. For me, the information if I finished a quest was not sufficiently conveyed. For example, I had one quest for heaven to “bring all characters to heaven for the round” and I did that for multiple rounds and the quest was unchanged. And because of the RNG, hell was significantly better off after I did that.