I seem to recall an interview in which Swen or someone else at Larian said they weren’t actually going to say or use the number of different permutations of endings because the number was so stupidly big no one would believe it. Sounds like someone might not have been on message, but that even though it wasn’t Larian who shared this number directly, that might have been the right call!
Personally, this isn’t something that exercises me at all. It just sounds like there are lots of possible things that can happen and that might influence exactly how the game, and the ending, play out. Which is great, though I’m unlikely to be counting exactly. It’s the journey that matters most to me, though of course I hope each of my playthroughs and characters does indeed get a finale that suits them.
Given the very low number of moving parts needed for 17k endings this makes more sense to me. If all the main characters have two different paths or could die and there are absolutely no other variables you hit 177,147 endings. Add half a dozen other considerations and you're at 11 million. From what we've heard of Larian's take on reactivity I wouldn't be shocked if the number hit quadrillions of variations of ending.