If a mechanic's purpose is to act as a temptation and resisting that temptation gets you an equal yet opposite mechanic as a reward it kind of undermines the function of the mechanic in the first place.
That isn't to say there can't be a sort of narrative balance between using it and not using it. Not using it just needs to reward the player in less tangible, measurable ways.
The easiest example is that to maximize your tadpole powers you need to need to harvest True Souls. This will lead you to kill your companions and probably bring you at odds with the Absolute anyway, as you'd want to harvest their True Souls too. You'll burn bridges on both sides of the conflict and likely end up alone against the world.
Or maybe you go halfsies and join the Absolute to harvest the tadpoles of the good companions to strengthen yourself and your evil-aligned companions. But now you're surrounded by power-hungry monsters who are proven willing to turn on their allies. You're also in the organization with the most access and knowledge of the tadpoles, but you're also at odds with all of Baldur's Gate with only the might of one insane cult to fight your war.
Or you resist the tadpole and maintain strong connections to your allies. Maybe you get betrayed by a few of the most evil companions, but you have total trust in the ones who've stuck around and have formed a powerful alliance with various NPC factions that are all uniting to protect Baldur's Gate from The Absolute. You might have less personal power by the end of the story than the first two options but narratively you're much stronger, with loyal allies and armies of good at your back.
But there could still be content for good characters too. Not rewards per se, but maybe something you can't find on evil paths. Maybe a new quest, some kinds of unique interactions, some another mechanic. Because so far it looks like the only benefit of going good will be the ending while getting to it will be far more barren compared to the evil one. Your journey will be worse and for many this is what matters the most. The journey and it will be barren and boring compared to the other given that Larians barely showed any content for good side and went back on their promise that people would get good Origins later as they first released Neutral and Evil ones to test waters apparently, but now the only good Origin is Karlach and Dark Urge is ultra evil path you can try to be good on.
And good companions you get outside of origins don't look much better, 2 of them are cameos from older games and 1 was not even planned to be a companion and is one due to fan demand. There is severe lack of content for good playthroughs from what it looks like from everything we see and it's not like you will completely lose your companions since Larian confirmed you can change them to be more evil so there is pretty much very little to lose on the journey on evil path while good one doesn't get almost anything exclusive to itself. And again, by content I don't mean more powers, rewards, I mean content as a whole that is unique to playing a good character. That's as if in WOTR you could become a Demon, Lich or Swarm, but there was no Angel, Aeon or Azata path.
