I see this as exactly Larian rewarding players for playing evil, by saying to them: Don't worry. There won't be any *real* consequences for doing all manner of evil things (including eating the tadpoles). In the end, you just have to do one thing, and all of the past is forgiven and forgotten and you get to be acclaimed as the "hero." That is utter b.s.
I don't think it's about rewarding evil (as the evil path is simply lacking in content compared to good), but rather a lack of commitment. You can play evil but won't be locked out of the good ending, you can play good but won't be locked out of the evil ending, even if this means your character does a 180° turn at some point.
This is not true for all the writing, notably when Shadowheart makes her choice there are no "take backs". A similar origin character concept, but better written.
But tbh, if you want a good amnesiac protagonist story, my recommendation would be Planescape Torment instead.
