There is a problem with Shadowheart that even aside from all datamining, there is literally nothing in the game to indicate that she is an evil character.
Just because she worships Shar would I put her neutral.
For the rest of the characters, it's quite simple. Due to the fact that Larian said there are no good characters at the start of EA.
I'm not sure how you can say that being a worshiper of a neutral evil diety doesn't indicate your own alignment.
"A neutral evil character is typically selfish and has no qualms about turning on allies-of-the-moment, and usually makes allies primarily to further their own goals. A neutral evil character has no compunctions about harming others to get what they want, but neither will they go out of their way to cause carnage or mayhem when they see no direct benefit for themselves."
That pretty much sums up every one of our companions.
