The difference, I think, is that choices in Dragon Age and similar games are presented to the player as very clear, discrete and equally valid options, while in older games, including Fallout, it's more like "weird shit the player did for the lulz", or things that the player didn't do optimally.
It's the same hole in the end though. Someone's playthrough is contradicted.
Gaider acted super excited about the god-child Morrigan thing on the Bioware forums but they can never, ever actually use that idea unless they choose to make that ending canon. They made that bed, sure, but at the end of the day I'd rather let a creator use what he's excited for than not.