We do find out from people that our tadpoles are different and we may not change as soon as expected. However this requires believing these people who are only speculating. No one knows for sure why our tadpoles are different, also why do we automatically believe people who are not experts on this? It could be considered "evil" or "selfish" to bring our potential walking bomb selves around others since we have the potential to destroy them at any point. It may be considered "selfish" to put our situation first but also "good" since we are trying to fix the situation as soon as possible so as to not risk others. It would probably be considered "good" to help the Tieflings but a Druid could find this "evil" because they put the grove first and see the Tieflings as a threat to its existence. One player may take the "good" path and ignore the situation because losing a few Tieflings along the road is a better outcome than potentially destroying all of them and the Druids as well. Another may take the "evil" path and save the Tieflings because they can use this to their advantage later. All of this stuff is a matter of perspective.
Indeed: motive, rather than action, is the informing factor in most cases - alignment isn't so much about what you do, as why you're choosing to do it. I do have to admit, though - that's a much more nebulous thing to pin down in a video game context, and that's the main reason, I think, why we always end up falling back on ascribing alignment to specific actions and disregarding the motive or reasoning behind it, in video games - the game can't track our reasoning, in most cases, so it ascribes a motive to you and judges you based on that... often to the detriment of immersion, sadly.
