The first is that I don't think BG3 really needs hard alignment in a story sense. I don't think that having alignment would improve the delivery of the story or its themes. I will insist that Wrath of the Righteous needed alignment because the whole point of the game is about becoming an extra-planar being, something that's more and less than human, and thus is more primal, more elemental, more ruled by these otherworldly ideals.
This is speculation about the story but it seems clear from what we've seen so far is that the tadpole is linked to the cult of the absolute in some manner. The tadpole is also linked to the shadow weave which is a creation of / extension of Shar. So while we're ordinary mortals were caught in a 4d chess game being played by gods and thus otherworldly ideals matter.
